I ran in the same "trap" after updating MariaDB and I also used
ALLOW_UNSUPPORTED_SYSTEM=true just to get it running. However, I also wanted to find out what was the real cause rather than "overwrite" all the time. In the official FreeBSD forum I found the hint that led me to the real cause:
Code:
freebsd-update -b <path to jail> IDS
This verified all files of the jail with the good-known ones and revealed that almost all system files in the jail were not up to date. After ensure all files matching were up to date with a supported FreeBSD version ports collection and MariaDB were running without any further error messages.