Strange looking certificate in macOS Keychain
I found a plausible explanation, the certificate is most probably related to studentd, see https://eclecticlight.co/2019/04/01/back-to-school-studentd-and-classroom-in-mojave-10-14-4/:


  Although run from a system LaunchAgent property list, studentd is run as the user from login. If you log into a user account which doesn’t yet have one, it creates a security certificate in that user’s login keychain, with a name starting with ‘member:’ followed by two UUIDs. The first of these is that user’s UserIdentifier given in ~/Library/studentd/AdHocConfiguration.plist, thus is that student’s identifier for the purposes of studentd. That certificate isn’t trusted, but trust is obtained later if the user connects that Mac to a Classroom system.