You mean you have not converted the database to utf8mb4 yet?
If true no wonder the question
It looks like the links he's posted links are to XenForo forum software from 2010. Not UBB.threads.
he also mentioned that he updated his forums to utf8mb4 a few months ago (in 2024) but has not said how.
https://www.ubbcentral.com/forums/u...52-characters-instead-of-utf8#Post266154@BaldEagle, when you updated your database, did you just change the collation, or did you actually change the data as well, by using UBB.thread's built in conversion upgrade tool (available since UBBT 7.7.4)