I like their build system, is very simple to use, based on shell scrips, and has some neat features, like ssh-ing into the machine that had a failed build, or spinning a build with a custom manifest file (useful when you need to iterate quickly).

Although it doesn't have all the "plugins" and other stuff that CI tools have today, it provides fairly "standard" points of integration

For more info: https://man.sr.ht/builds.sr.ht/

I agree the website is a bit confusing at first, but after spending a couple of hours on it you can easily see how it's organised, for example to display branches and files it uses the more basic git terminology (e.g. main branch -> tree, list of commits -> log, branches and tags -> refs)