On the off chance there are new tooters like myself who are also #GalaxyFold users, I've found the web app is actually the optimal way to use Mastodon on Fold.
Use Chrome to add it to Home with its own shortcut, & the great payoff is that when opening into full screen mode it'll switch seamlessly into multi-column mode (if enabled).
I like Tusky too, but the web app is the best option for an open Fold right now I think.