I missed my oasis dearly but I couldn’t wait anymore and got a Kobo Libre (not sure the exact model, th color one); it’s pretty much as good, only thing i miss is the dual battery system.
Koreader is well supported and has all the features you mention.
This setup feels cumbersome, since you also have to manually track which items you have read. Kobo seems to offer better features in this sense (better than a jail broken kindle), however I like the build of my Kindle Oasis 2 too much.
This gives you full access to upload whatever ebook you want (SSH, WebDav, Syncthing, ...) and it can fetch RSS feeds (i use it with FreshRSS.)
PS. The (very old) Kindle Oasis is still the best device there is to read on in my opion. Which is crazy, since it was released from 2016-2019...
It has 2 phyisical buttons to turn the page, and an ambient light sensor to auto adjust the brightness, and a 300 PPI display.
I'm still "waiting" for a better / equal device to be released.
[1] https://kindlemodding.org/kindle-models.html
[2] https://github.com/koreader/koreader
Koreader is well supported and has all the features you mention.