Investigate (drop-in) alternatives to FluxBB

[petecooper]

https://github.com/MioVisman/FluxBB_by_Visman

https://github.com/forkbb/forkbb

We're about a T minus 14 months for PHP 8.1 security support ending, and our current FluxBB instance is pegged to PHP 8.1. An interim measure would be to investigate a drop-in replacement with newer PHP support, such as the options above.

Longer term, we can consider a new forum scaffold when Textpattern 5 is nearing release, but we're realistically a few years away from that at present.