Tools & Settings > Advisor > Performance shows that HTTP/2 is disabled after upgrading to Plesk Obsidian:
CONFIG_TEXT: HTTP/2 is not configured
HTTP/2is shown as enabled via CLI:
# plesk bin http2_pref --status
This has been reported as bug ID EXTADVISOR-752 which will be fixed in future updates.
This is a cosmetic bug and can be safely ignored.