Switching between Tabs
By default on Linux the keybindings Alt + number are used to switch between tabs. On Windows and MacOS however Control and Command are used instead.
You can change this via the ctrl-number-to-switch-tabs extensions. After installation go to extensions specific options and change the keybinds to use Alt instead.
Reference: https://www.reddit.com/r/firefox/comments/s9ey4g/any_way_to_change_switch_tab_keybind/