Wanted to report that this Whoops \ Exception \ ErrorException (E_WARNING) Illegal string offset 'fail2ban_ban_time' - #56 by sentinelace seems to be still an issue.
Restored from a backup of FreePBX 16 to brand new hardware that’s had a clean FreePBX 16 install and fail2ban was failing to start. After seeing that thread I went to check and /etc/fail2ban/filter.d/zulu.conf was missing. Copying one from a working system resolved the issue for us on this restore.