I maintain a fork of tt-rss[0] that I use to follow blogs, podcasts, and YouTube. I wrote a podcatcher that used the back-end database, too.
I forked it back in 2005 because the maintainer wasn't interested in the direction my patches were going. My version has diverged dramatically from the current version.
I have no idea how many hours I've put into it over 19 years. It has needed surprisingly little care and feeding (which I'd attribute to it being a simple PHP app).
Edit: I also maintain a set of scripts to import my SMS from phone backups into my IMAP mailbox. Having a single place to search for my written communication is wonderful.
Out of curiosity, what are the design changes you've introduced into TT-RSS? I've been using it for about 15 years as well, and often get frustrated with the over-opinionated design philosophy of the project myself, so have made a couple of tweaks to my own install, but nowhere to the point of maintaining an entire fork.
I haven't done a ton to it. Mainly I have my fork because I got the features I needed when mine diverged from the mainline back in late '05 and I never cared to keep porting my changes forward.
Initially the changes were for handling enclosures. The developer had no interest in supporting them. I wanted to use tt-rss as a podcatcher. That necessitated adding some database schema (tracking enclosure URLs) and UI (a "request download" button in the entry list and entry detail panes for those podcasts where I only download selected episodes, a "download all enclosures" checkbox in the preferences UI for podcasts where I want every episode downloaded).
I also added schema for multiple users to sharing the same database. It was basically per-user preferences and read/unread flags. My grand intention was to add "social" features and eventually a suggestion algorithm. The developer's reaction re: "social" features was, basically, "Why?". (I see that the project has since gained multi-user support...)
I never did much with my multi-user schema. I never even switched my production copy over to it. Amusingly, I've ended up running three separate instances support my blog reading, podcatcher, and TV computer (Youtube feeds). If I'd finished the multi-user work I could be using that instead.
That was the end of my interaction w/ the developer.
In later years I added virtual feeds for the podcatcher and tt-rss itself to report errors downloading or parsing feeds.
I forked it back in 2005 because the maintainer wasn't interested in the direction my patches were going. My version has diverged dramatically from the current version.
I have no idea how many hours I've put into it over 19 years. It has needed surprisingly little care and feeding (which I'd attribute to it being a simple PHP app).
I've used it nearly daily in the last 19 years.
[0] https://tt-rss.org/
Edit: I also maintain a set of scripts to import my SMS from phone backups into my IMAP mailbox. Having a single place to search for my written communication is wonderful.