Newpipe and Redreader for reddit are my 2 favourite apps on Fdroid. Amaze file manager is also pretty sleek for an Fdroid app. Dns66 is great for adblocking when you are not rooted. Termux is a must have for those who need a terminal. Osm+ is a decent maps option and Mupdf is a fast and minimal reader for pdf files.
Fdroid is great for open source apps especially when you are trying to avoid shady behavior by apps, but since Android itself is full of shady behavior and dark patterns it's at best a bandage on a severely wounded patient.
Slide for reddit is another reddit client. Fully open source under GPLv3, nice looks and hi designed very well such that you never have to reach for keys at the bottom. Wholeheartedly recommended.
The last time i tried Amaze i found the large logo in the sidebar irksome (especially as there was no way to hide the sidebar on a tablet), and it seemed to have trouble generating thumbnails when opening at a directory stuffed with photos or videos (it would generate a few, then stop, then pick up again once you scrolled, skipping 2-3 near where it last stopped etc).
Fdroid is great for open source apps especially when you are trying to avoid shady behavior by apps, but since Android itself is full of shady behavior and dark patterns it's at best a bandage on a severely wounded patient.