I am looking for an RSS reader that is web based and preferably FOSS, I am trying to move from Vivaldi to Waterfox but I am using the Vivaldi RSS reader and need to switch to something else.

https://www.reederapp.com/

If you're ok self-hosting, I use www.freshrss.org

Why are you moving on from Vivaldi?

This is a Mac app and not web-based

vivaldi is proprietary, bonus evil points for being chromium-based

I ahve used capy reader on android, available on Fdroid. Currently, I am using Nextcloud news as my RSS, works everywhere, web clients, android clients, all FOSS.

I've been on FreshRSS for over a year. Works well even on shared hosting. https://www.freshrss.org/

FreshRSS with Capy Reader on mobile .

I self host FreshRSS, I can recommend this one easily

This has felt like the perfect combination to me for a few months

I like FreshRSS.

Please add cross-references when you post the same post to two communities at the same time. That way, people can find the other comments and discussion.

Thank you for the Capy Reader recommendation

It is also (as far as I can tell) proprietary

I've been using Feeder https://f-droid.org/packages/com.nononsenseapps.feeder/ Works for my needs, but I haven't explored much.

https://www.commafeed.com/