Ok, I’ve now had time to check this out. Android Firefox is set to strict Enhanced Tracking Protection which says offers fingerprint protection. If that is capping my refresh rate, then I can’t see it. Scrolling is smooth.
In contrast, Mull is distractingly flashy when scrolling. There is absolutely something different going on here.
Check out Wiremin https://play.google.com/store/apps/details?id=com.wiremin.im
It’s pretty private but when I uninstalled the community was getting sparse and notifications were slow. Might be better or worse these days.