Everyone probably knows of Izzy -
His Neo Store is pretty awesome as an fdroid replacement for diff repo's etc (a lot even included, just enable or disable what you want/dont)
ffshare is my goto for quickly reducing image sizes when you just want to send a photo quickly.
Cams is a brilliant actively developed rtsp viewer (spare tablet + cams = light weight at a glace monitoring etc)
Saw Markor above, it is fantastic - Quilpad is my 2nd choice for markdown..
Vivaldi is a decent cross platform browser - I do have it installed on my phones though Vanadium is the best by far - Vivaldi can be useful though when you want to sync browser sessions to your laptop etc (*nix in my case)
Bitwarden is nice too - on *nix can try Goldwarden (made by one of the main devs of Bitwarden - he very good at crypto as well)