The Fairphone OS release notes for version A.157 states that a connection problem with PEAP-protected networks has been fixed. This might be the problem discussed in this topic, so it would be interesting to know if people still have this problem on the latest Fairphone OS.
This fix is not mentioned in the FP4 release notes, so if the FP4 problem discussed in this topic is caused by the same issue, it might not yet be solved for the FP4.