I have also had issues with type C connection reliability, but every single time so far it has been an issue with the cable. I thought that the port on my phone of 4+ years was dying, the connection felt loose and it would charge unreliably, but changing out the cable has completely removed all issues.
Posteo has no custom domain support, deal breaker for me. As far as I understand they don't support IMAP in order to keep their encryption working, and I believe others like Proton do the same thing. Since their webapp is good and they even have an official client on Fdroid, I don't think it's a big deal
I'm trying to move away from needing a VPN to connect to make it simpler for less technically inclined family members