Hi !
I'm sorry to reply in english, but i think i vae valuable information for you, and my german is ok to read an dunderstand you, but not to answer you.
So, here is the situation as of today :
- mausberry is supported https://github.com/recalbox/recalbox-os/wiki/Mausberry-Switch-Power-On-off-(EN)
- power on/off/reset and led are supported through GPIO https://github.com/recalbox/recalbox-os/wiki/Add-a-start-stop-button-to-your-recalbox-(EN)
- most adatpers SNES -> USB should be supported
- you can use the gamecon driver if you want to map your original SNES controllers without using any USB converter. You need to read the doc and do the right wiring on GPIO https://github.com/recalbox/recalbox-os/wiki/Gamecon-controllers-(EN) (dunno if this has been translated to German, you can still check)
I'm not sure i understood correctly the MCP23017 part ... What i can say is that it is supposed to work but I don't know if the module we compile on Recalbox has this feature. I think it does have it, should ask @digitalLumberjack. I haven't checked either if you can use both MCP23017 with gamecon.
Hope i could be of any help