Visible's tethering is limited to 5Mbps (according to their pricing page). Have you been getting more than 5Mbps tethering? Do you do anything to get around tethering speed limits?
Deprioritization can be hard in some areas. Verizon has the most customers and the least spectrum at the moment.
I think I've gotten more than 5mbps (or at least was for a time) - I haven't done anything, but I might be wrong about this (I don't rely on tethering most of the time so haven't noticed).
IIRC a long time ago all of Visible's data speed was capped at 5mbps and that was the 'tradeoff' of the low cost service in addition to deprioritization. They eventually dropped that cap, but it's possible it still exists for tethering.
I will plug Starlink for those that can get it though - not mobile yet, but we went from a crappy calnet connection to a stable 50+ sometimes 150+ mbps connection. When they get it working across cells (which Musk tweeted interest about) it'd be a pretty sweet option for an RV. If you're out in the boonies though and looking for stable home internet, it can't be beat (as long as you have a clear view of the sky).
Deprioritization can be hard in some areas. Verizon has the most customers and the least spectrum at the moment.