I tested threema through waydroid.
It works, but without camera access ( Anyone Successfully Run WayDroid on Librem 5? )
I followed this way:
- Install waydroid ( https://source.puri.sm/-/snippets/1198 )
- Then in waydroid : F-droid ( https://f-droid.org/ )
- Then in F-droid install Threema-libre ( https://threema.ch/en/faq/libre_installation )
Share us your feelings !