Selfhosted

FreshRSS has been amazing, as you said, other readers have other goals in mind and seems RSS is just an add-on.

On Android's also there are no good clients, I've been using the PWA which is good enough.
There are several extensions for mobile menu improvements, I have Smart Mobile Menu, Mobile Scroll Menu and Touch Control (it works great on Firefox, but not on brave, it's too sensitive there, so YMMV).

There's also ReadingTime, but there are feeds which don't send the whole body of the post, so you might only see a 1minute read because of that.

The extension AutoTTL processes the feeds and makes them update only when it's more likely for them to get new items instead of every X minutes configured by FreshRSS.
Still there's a problem when the MaxTTL happens, all feeds are allowed to be updated and you might hit some rate limits, so I developed a rate limiter. Still there's a problem with AutoTTL because how extensions are loaded and with the http code reported by FreshRSS.

I found this project which receive the emails of newsletters and turns them into a RSS feed, I've only used it for one feed and I've only received one entry, not sure if the newsletter is that bad or if the site struggles to receive/show them. Haven't tried something it.
https://github.com/leafac/kill-the-newsletter

There's also this repo linking a lot of sites with feeds, and some sites which don't offer feeds directly are provided via feedburner (which seems it's a Google service and wikipedia says "primarily for monetizing RSS feeds, primarily by inserting targeted advertisements into them", so use those at your own discretion) https://github.com/plenaryapp/awesome-rss-feeds