The issue here is because of Ubuntu following the OpenSSL 3 migration, and having a default security level of 2. The default security levels can be explained here (under "Default Callback Behavior") explaining what each level means in OpenSSL 3.0. Ubuntu uses the default level of 2 on the versions of OpenSSL it ships.
As of Ubuntu 22.04 Jammy, OpenSSL uses the default security level of 2. In the OpenSSL 3.0 migration guide changes were made to the OpenSSL default of level 1 such that "X509 certificates signed using SHA1 are no longer allowed at security level 1 and above." Unfortunately, because SHA1 certificates are 'insecure' now, you have to drop your config down to the security level of 0 which lets everything be accepted. Which is insecure, but until your IT group updates the certs, you don't have much of a choice here.
Per this answer, you should be able to adjust your configuration to use the older security defaults. I've adapted those instructions here.
/etc/ssl/openssl.cnf file. At the beginning of the file, add this:
openssl_conf = default_conf
[ default_conf ]
ssl_conf = ssl_sect
system_default = system_default_sect
CipherString = DEFAULT:@SECLEVEL=0
Then reboot your system to make sure that the security levels are properly set, and test connecting. You should no longer have this issue. Be advised that this reduces the overall security of your system and may leave you open to vulnerabilities in older protocols and security ciphers in use on older sites or intentionally malicious sites.
Ultimately, the IT group of your university needs to reissue the certificate with a SHA256 signature and apply it to the eduroam infrastructure on their end. The aforementioned approach to reduce the security defaults is not guaranteed to be secure since SHA1 signed certificates are considered deprecated now by SSL standards. You should remove the configuration that is done here as soon as the IT team updates their certificates.
Alternatively dont use a cert with your eduroam connection in the interim.