Dear @ptrenz, thank you so much, this is really helpful! So Nibe seems very suitable for me. I will check out, Vaillant, too.
Regarding EEBus: @M_Lange wrote above that VenusOS 3.80 will support EEBus. The release notes suggest that initially, only MPC is supported. Am I right @ptrenz that more functions will follow?
Cheers and thank you for the really helpful guidance!