@ttpost Yes, had changed.
openssl s_client -connect imap.vivaldi.net:993 | openssl x509 -dates -fingerprint depth=2 C = US, O = Internet Security Research Group, CN = ISRG Root X1 verify return:1 depth=1 C = US, O = Let's Encrypt, CN = R3 verify return:1 depth=0 CN = imap.vivaldi.net verify return:1 notBefore=Jul 12 05:52:54 2021 GMT notAfter=Oct 10 05:52:53 2021 GMT SHA1 Fingerprint=8A:02:13:E0:30:E9:A9:0C:64:C6:6B:69:A6:99:22:FC:10:1C:D1:20