This setting is available in - Avast - Menu - Settings - Scam Guardian - Enable QUIC/HTTP3 scanning.
Please note that disabling this feature will limit some scanning ability of Avast Web Shield (Web Guard).
We are currently investigating this issue, but it would be helpful if affected users could provide us with custom logs as per this post: Avast block facebook from opening - #15 by prokopes_
(we recognize these steps are rather complex, so we respect if you don’t wish to spend time on this log collection)