I’m making use of a self-hosted Nextcloud instance for this purpose actually. While I wouldn’t necessarily recommend it just for the purposes of RSS, it’s a nice addition to the platform for someone who happens to be running an instance for other reasons already. Most of the web-based RSS reader solutions I’ve come across relied on advertising or other premium membership models to support the service, so an alternative would have to be pretty damn compelling for me to transition away from Nextcloud and start subjecting myself to ads again.