In addition the display in the menus, you can use the keyboard settings' shortcuts section to see the global keybindings and add new ones either globally or within a particular app.
There's also a pretty comprehensive version here:
https://support.apple.com/en-us/HT201236
> Second issue is that all the keymappings are different to Windows/Linux/BSD/AnythingElse.
There's a bit of early GUI history which explains most of this – MacOS was the earliest mainstream GUI and they had guidelines pretty early on which most Mac applications use. A decade or so later IBM decided they needed to create their own standard (Common User Access) which they pushed to get implemented on OS/2, Windows, and other operating systems.
Mac users continued to want what they were familiar with, and applications which were business-focused in the late 80s-90s got CUA, and a whole lot of other software got some agglomeration of whatever the developers were familiar with and/or the toolkit they were using provided by default.
> I'd had carpal tunnel (and it's kind of a chronic thing), so using a touchpad to point-and-click is literally painful for me. A mouse is okay, but it seems to be impossible to connect bluetooth devices on macOS without using the touchpad.
Two ways:
1. If it's an Apple mouse with a lightning port, plug it in once with the cable.
2. It sounds like you might not have activated the accessibility setting which toggles tab navigation from only navigating between text fields to all controls. Use Control-F7 to toggle that and then:
1. Open settings – you can use Spotlight via Command-Space or Option + either the sound or display adjustment keys to open Settings without using a pointing device
2. Either navigate the icons or use search to select Bluetooth
3. Hit tab, the default focus ring will be on the “Turn Bluetooth Off” button if full control navigation mode is enabled.
4. Hit tab, focus will now be on the devices list
5. If your mouse is pairable, it'll show up with a connect button. Use the arrow keys to select that line and hit enter.