This is more to document my experience upgrading from v0.16.0 beta to v1.0.4, which also required me to update the php version.
php flarum info the php version came up as v8.0.8.
However before upgrading the flarum dashboard would show 7.3.
After a bit of digging, the nginx sites-available
Had to update it to:
Hope this can help someone else that's rather new and stuck on why it isn't updating.