diff --git a/Build-exe-and-msi.py b/Build-exe-and-msi.py
index adc04432..71e1eace 100644
--- a/Build-exe-and-msi.py
+++ b/Build-exe-and-msi.py
@@ -28,6 +28,9 @@ if sys.platform == 'win32':
 
 else:
     raise AssertionError(f'Unsupported platform {sys.platform}')
+
+# This added to make mypy happy
+assert sys.platform == 'win32'
 ###########################################################################
 
 ###########################################################################
diff --git a/EDMarketConnector.py b/EDMarketConnector.py
index b6bbcf11..b9c7bdf2 100755
--- a/EDMarketConnector.py
+++ b/EDMarketConnector.py
@@ -1617,10 +1617,11 @@ class AppWindow(object):
                                                                  monitor.system and
                                                                  tk.NORMAL or tk.DISABLED)
 
-    def ontop_changed(self, event=None) -> None:
-        """Set main window 'on top' state as appropriate."""
-        config.set('always_ontop', self.always_ontop.get())
-        self.w.wm_attributes('-topmost', self.always_ontop.get())
+    if sys.platform == 'win32':
+        def ontop_changed(self, event=None) -> None:
+            """Set main window 'on top' state as appropriate."""
+            config.set('always_ontop', self.always_ontop.get())
+            self.w.wm_attributes('-topmost', self.always_ontop.get())
 
     def copy(self, event=None) -> None:
         """Copy system, and possible station, name to clipboard."""
@@ -1760,13 +1761,14 @@ class AppWindow(object):
         with open(f, 'wb') as h:
             h.write(str(companion.session.capi_raw_data).encode(encoding='utf-8'))
 
-    def exit_tray(self, systray: 'SysTrayIcon') -> None:
-        """Tray icon is shutting down."""
-        exit_thread = threading.Thread(
-            target=self.onexit,
-            daemon=True,
-        )
-        exit_thread.start()
+    if sys.platform == 'win32':
+        def exit_tray(self, systray: 'SysTrayIcon') -> None:
+            """Tray icon is shutting down."""
+            exit_thread = threading.Thread(
+                target=self.onexit,
+                daemon=True,
+            )
+            exit_thread.start()
 
     def onexit(self, event=None) -> None:
         """Application shutdown procedure."""
diff --git a/config/linux.py b/config/linux.py
index 04087b32..5d543d3f 100644
--- a/config/linux.py
+++ b/config/linux.py
@@ -3,7 +3,6 @@ import os
 import pathlib
 import sys
 from configparser import ConfigParser
-from typing import List, Optional, Union
 
 from config import AbstractConfig, appname, logger
 
@@ -18,7 +17,7 @@ class LinuxConfig(AbstractConfig):
     __unescape_lut = {'\\': '\\', 'n': '\n', ';': ';', 'r': '\r', '#': '#'}
     __escape_lut = {'\\': '\\', '\n': 'n', ';': ';', '\r': 'r'}
 
-    def __init__(self, filename: Optional[str] = None) -> None:
+    def __init__(self, filename: str | None = None) -> None:
         super().__init__()
         # http://standards.freedesktop.org/basedir-spec/latest/ar01s03.html
         xdg_data_home = pathlib.Path(os.getenv('XDG_DATA_HOME', default='~/.local/share')).expanduser()
@@ -42,7 +41,7 @@ class LinuxConfig(AbstractConfig):
 
         self.filename.parent.mkdir(exist_ok=True, parents=True)
 
-        self.config: Optional[ConfigParser] = ConfigParser(comment_prefixes=('#',), interpolation=None)
+        self.config: ConfigParser | None = ConfigParser(comment_prefixes=('#',), interpolation=None)
         self.config.read(self.filename)  # read() ignores files that dont exist
 
         # Ensure that our section exists. This is here because configparser will happily create files for us, but it
@@ -85,7 +84,7 @@ class LinuxConfig(AbstractConfig):
         :param s: str - The string to unescape.
         :return: str - The unescaped string.
         """
-        out: List[str] = []
+        out: list[str] = []
         i = 0
         while i < len(s):
             c = s[i]
@@ -107,7 +106,7 @@ class LinuxConfig(AbstractConfig):
 
         return "".join(out)
 
-    def __raw_get(self, key: str) -> Optional[str]:
+    def __raw_get(self, key: str) -> str | None:
         """
         Get a raw data value from the config file.
 
@@ -119,7 +118,7 @@ class LinuxConfig(AbstractConfig):
 
         return self.config[self.SECTION].get(key)
 
-    def get_str(self, key: str, *, default: str = None) -> str:
+    def get_str(self, key: str, *, default: str | None = None) -> str:
         """
         Return the string referred to by the given key if it exists, or the default.
 
@@ -134,7 +133,7 @@ class LinuxConfig(AbstractConfig):
 
         return self.__unescape(data)
 
-    def get_list(self, key: str, *, default: list = None) -> list:
+    def get_list(self, key: str, *, default: list | None = None) -> list:
         """
         Return the list referred to by the given key if it exists, or the default.
 
@@ -168,7 +167,7 @@ class LinuxConfig(AbstractConfig):
         except ValueError as e:
             raise ValueError(f'requested {key=} as int cannot be converted to int') from e
 
-    def get_bool(self, key: str, *, default: bool = None) -> bool:
+    def get_bool(self, key: str, *, default: bool | None = None) -> bool:
         """
         Return the bool referred to by the given key if it exists, or the default.
 
@@ -183,7 +182,7 @@ class LinuxConfig(AbstractConfig):
 
         return bool(int(data))
 
-    def set(self, key: str, val: Union[int, str, List[str]]) -> None:
+    def set(self, key: str, val: int | str | list[str]) -> None:
         """
         Set the given key's data to the given value.
 
@@ -192,7 +191,7 @@ class LinuxConfig(AbstractConfig):
         if self.config is None:
             raise ValueError('attempt to use a closed config')
 
-        to_set: Optional[str] = None
+        to_set: str | None = None
         if isinstance(val, bool):
             to_set = str(int(val))
 
diff --git a/hotkey/darwin.py b/hotkey/darwin.py
index a053a55f..cbf9d260 100644
--- a/hotkey/darwin.py
+++ b/hotkey/darwin.py
@@ -3,6 +3,7 @@ import pathlib
 import sys
 import tkinter as tk
 from typing import Callable, Optional, Tuple, Union
+assert sys.platform == 'darwin'
 
 import objc
 from AppKit import (
@@ -36,7 +37,7 @@ class MacHotkeyMgr(AbstractHotkeyMgr):
 
     def __init__(self):
         self.MODIFIERMASK = NSShiftKeyMask | NSControlKeyMask | NSAlternateKeyMask | NSCommandKeyMask \
-                            | NSNumericPadKeyMask
+            | NSNumericPadKeyMask
         self.root: tk.Tk
 
         self.keycode = 0
diff --git a/hotkey/linux.py b/hotkey/linux.py
index 9a60515f..927c4d26 100644
--- a/hotkey/linux.py
+++ b/hotkey/linux.py
@@ -1,7 +1,11 @@
 """Linux implementation of hotkey.AbstractHotkeyMgr."""
+import sys
+
 from EDMCLogging import get_main_logger
 from hotkey import AbstractHotkeyMgr
 
+assert sys.platform == 'linux'
+
 logger = get_main_logger()
 
 
@@ -20,6 +24,37 @@ class LinuxHotKeyMgr(AbstractHotkeyMgr):
         """Unregister the hotkey handling."""
         pass
 
+    def acquire_start(self) -> None:
+        """Start acquiring hotkey state via polling."""
+        pass
+
+    def acquire_stop(self) -> None:
+        """Stop acquiring hotkey state."""
+        pass
+
+    def fromevent(self, event) -> bool | tuple | None:
+        """
+        Return configuration (keycode, modifiers) or None=clear or False=retain previous.
+
+        event.state is a pain - it shows the state of the modifiers *before* a modifier key was pressed.
+        event.state *does* differentiate between left and right Ctrl and Alt and between Return and Enter
+        by putting KF_EXTENDED in bit 18, but RegisterHotKey doesn't differentiate.
+
+        :param event: tk event ?
+        :return: False to retain previous, None to not use, else (keycode, modifiers)
+        """
+        pass
+
+    def display(self, keycode: int, modifiers: int) -> str:
+        """
+        Return displayable form of given hotkey + modifiers.
+
+        :param keycode:
+        :param modifiers:
+        :return: string form
+        """
+        return "Unsupported on linux"
+
     def play_good(self) -> None:
         """Play the 'good' sound."""
         pass
diff --git a/hotkey/windows.py b/hotkey/windows.py
index 0bc54d1a..8a1c7acd 100644
--- a/hotkey/windows.py
+++ b/hotkey/windows.py
@@ -2,6 +2,7 @@
 import atexit
 import ctypes
 import pathlib
+import sys
 import threading
 import tkinter as tk
 import winsound
@@ -12,6 +13,8 @@ from config import config
 from EDMCLogging import get_main_logger
 from hotkey import AbstractHotkeyMgr
 
+assert sys.platform == 'win32'
+
 logger = get_main_logger()
 
 RegisterHotKey = ctypes.windll.user32.RegisterHotKey
diff --git a/myNotebook.py b/myNotebook.py
index 1989141f..30f95274 100644
--- a/myNotebook.py
+++ b/myNotebook.py
@@ -76,7 +76,8 @@ class Label(tk.Label):
     """Custom tk.Label class to fix some display issues."""
 
     def __init__(self, master: Optional[ttk.Frame] = None, **kw):
-        if sys.platform in ['darwin', 'win32']:
+        # This format chosen over `sys.platform in (...)` as mypy and friends dont understand that
+        if sys.platform == 'darwin' or sys.platform == 'win32':
             kw['foreground'] = kw.pop('foreground', PAGEFG)
             kw['background'] = kw.pop('background', PAGEBG)
         else:
diff --git a/protocol.py b/protocol.py
index 290a7031..f0e1b4a8 100644
--- a/protocol.py
+++ b/protocol.py
@@ -121,9 +121,13 @@ elif (config.auth_force_edmc_protocol
           and not is_wine
           and not config.auth_force_localserver
       )):
+    # This could be false if you use auth_force_edmc_protocol, but then you get to keep the pieces
+    assert sys.platform == 'win32'
     # spell-checker: words HBRUSH HICON WPARAM wstring WNDCLASS HMENU HGLOBAL
     from ctypes import windll  # type: ignore
-    from ctypes import POINTER, WINFUNCTYPE, Structure, byref, c_long, c_void_p, create_unicode_buffer, wstring_at
+    from ctypes import (  # type: ignore
+        POINTER, WINFUNCTYPE, Structure, byref, c_long, c_void_p, create_unicode_buffer, wstring_at
+    )
     from ctypes.wintypes import (
         ATOM, BOOL, DWORD, HBRUSH, HGLOBAL, HICON, HINSTANCE, HMENU, HWND, INT, LPARAM, LPCWSTR, LPVOID, LPWSTR, MSG,
         UINT, WPARAM
diff --git a/tests/config/_old_config.py b/tests/config/_old_config.py
index 0226bc36..211c1e72 100644
--- a/tests/config/_old_config.py
+++ b/tests/config/_old_config.py
@@ -1,3 +1,4 @@
+# type: ignore
 import numbers
 import sys
 import warnings