I think the ethos of open source flips this thinking. You should not trust. Microsoft may not be noting down your banking details, but you actually don’t and can’t know if it is. What it is doing is storing other personal data, because that is in its policies. Now, to what extent it takes advantage of this capability and permission, it is again unknown and unknowable.
Microsoft may be a big corp, but some distros are the backbone of highly critical systems, and collectively they run the vast majority of servers.
You don’t “trust” your distro. Or your laws. Everything being done is in the open, so you can see for yourself. If you lack the knowledge to do that, there are others who are doing it and many are sharing what they find. You will “trust” on some level, because of its reputation, how established it is, but trust here means something very different from letting a huge blob of unknown code do whatever it does because I trust you.
Yes, Fossify came precisely as a continuation for the Simple apps. The https://github.com/FossifyOrg org and the website https://www.fossify.org/ are linked from the F-Droid metadata so they should be legit as well.
See also: https://f-droid.org/2024/01/04/twif.html