[quirino]

I don't have a ± key. I'm using swaywm which seems to have no compose key set by default, I've tried all the common ones and they don't act as such.

I haven't been able to detect any pattern to what triggers this, at all. It is always "±".

[Suppafly]

You could probably set up some keylogging to see if anything special is happening before it, it'd also let you know for sure if it's a keyboard issue or not.

[cryptonector]

Maybe there's buggy malware involved?

[seanthemon]

Buggy malware is jusy a feature