Some requirements:

FOLDERS - I need folders and the ability to view all feeds within a folder at once.

FOSS - I don't want to give corporate ghouls my money and my privacy. I'll pay a foss creator if its a one-time fee or offers a reasonable annual subscription.

MULTI-PLATFORM - iOS, Android, Web. I have multiple devices and only want one app for them all. If something is Web-only, that will do.

Thank you.