The only game I am not able to make it work on Linux is “The Sims 4”. After installing it on Steam, when clicking on Play, it runs the EA app in the background and tries to start the game, but it doesn’t load. Any suggestion?

If you can hide an old small android phone with a a SIM card in your bike, you can use FindMyDevice (FMD) available in f-droid.

If not you can use some pet tracking device, like FindMyCat. It’s a small opensource device in a collar where you need to plug in a SIM card.

But if you want a device which uses low power Bluetooth / mesh connection and which doesn’t require SIM card nor GPS. Then I don’t know any alternative which is not a privacy nightmare.