Context

Bitchat is an open source tool that, among other things, lets you communicate with the devices around us, without a network, via Bluetooth. GitHub repo: https://github.com/permissionlesstech/bitchat I personally installed it on my Redmi Note 11S via the Komi Store platform, an open source alternative to the Play Store, with this specific repo for Android. (it can matter depending on the apps you install, because Komi Store removes the Google dependency by default, so things like push notifications may not work out of the box. That’s not the problem here, it’s just for information.)

Problem

Even though everything was configured properly (Bluetooth / Location turned on, battery restriction removed, etc.), it didn’t work.
I could use it, but not in Bluetooth mode.

Solution

I learned, via AI, that there can be a bug the first time if you open the app without having turned on Bluetooth and location beforehand. Just go to the phone’s settings, find the app and tap “Force stop”. After that, relaunch it and the problem is solved.
That’s what worked for me, at least.

If you don’t want the hassle of digging through the settings, I imagine a simple restart of the phone works too…