Go to your phone homescreen and look at the app dock (the bottom row that contains some apps and stays the same when you switch pages).
Which are yours? Any FOSS apps?
In my case, they are FDroid, Signal, Threema, Firefox and the defaul Samsung camera app. So, 80% FOSS…
Well as I don’t have a dock in Niagara Pro I just go on with the apps I pinned:
Telephone, standard dailer from android : ✔️
WhatsApp, eeeeh: ❌ ❌ ❌
Discord: ❌
Firefox: ✔️
Proton Mail: well not FOSS (at least the paid tiers) but OSS
Proton Calendar: same thing
Jerboa: ✔️
Tusky: ✔️
Grayjay: I guess yeah to both (with license) ✔️
M.A.L.P: check and check ✔️