So the problem, besides having to delete the non working Supercollider install, is that the name of the UGens are not Input and Output as stated in the README but In and Out.
In /usr/local/share/SuperCollider/SCClassLibrary/Common/Audio/bela/BELAUGens.sc
AnalogIn : UGen
AnalogOut : UGen
/home/ulrich/.local/share/SuperCollider/Extensions/bela-remote/Classes/BELAUGens.sc
AnalogInput : UGen
AnalogOutput : UGen
I'll notify it on the git for the extensions.