Immediately after switching the page, it will work with CSR.
Please reload your browser to see how it works.
Probably not really usable for anyone except myself but here is the code for my reader: https://github.com/vborovikov/news
I guess the only thing it doesn't have that a SaaS offering could do would be some sort of recommendation engine (which I have no interest in).
From a desktop app's point of view, I have tried liferea for a while and liked it a lot.
I'm not using anymore though, because the websites I used to follow went behind captcha mechanism(s) and cannot fetch their feed any longer which saddens me just by thinking about it.
Though it may not meet your criteria around infinite retention. The developer has written about their philosophy on that here: https://inessential.com/2018/10/13/netnewswire_article_age_l...