I remember doing this on Reddit Sync years ago by combining this option,
Settings shortcut: History > Mark posts as read on scroll
With something like this option,
Settings shortcut: General > FAB action
Set the FAB to hide read posts. The main difference to how I had it working in the past is that with this, you must use the floating action button to periodically purge this content, where as I’m sure I had it working automatically before.
Yeah I don’t like Microsoft but like Office, I just run offline pirated version of their main programs. It’s like how I avoid Google for 70% of options but absolutely love Google Maps and Google Translate.