From what I read, Android 9 and 10 should still include the clatd translator for NAT64 services. Without it, Android apps that aren’t IPv6-compatible will also stop working.
Could you raise an issue with Fairphone Support about this just to get this clarified?
If someone can confirm that FP3 Android 9 and/or the FP2 indeed translate IP addresses on the Deutsche Telekom network, the issue can be added to this list.