So what did the trick for me was to install the stock Fairphone Android and then iodeOS again. I think it has to do with some firmware/driver shit. I made sure to not the latest version, but the one prior to the last release to match iodeOS’ security patch level, as I was scared of bricking my device. This can happen if you try to relock and downgraded your security patch level.
So far I was only able to test the microphone via Discord, but that does work now and did not before.