No "Use system certificates" when trying to connect to WiFi
I solved this problem at my university (not Eduroam) by installing a CA certificate in Android (8). It then becomes a choice in the CA Certificate menu and you can sign in.

Hopefully, you can find out from the IT people where is the CA Certificate to download to your Android. 

I think choosing "Don't validate" is unwise, and that's actually what many university IT web sites advise (Google finds the instructions easily).

Edit: for Eduroam, there's an app that reportedly solves the problem for Android 8.