alt Hacker NewsI tend to just rely on the platform installers, then write my own process scripts to handle the work beyond the runners. Lets me exercise most of the process without having to (re)run the ci/cd processes over and over, which can be cumbersome, and a pain when they do break.
The only self-hosted runners I've used have been for internalized deployments separate from the build or (pre)test processes.
Aside: I've come to rely on Deno heavily for a lot of my scripting needs since it lets me reference repository modules directly and not require a build/install step head of time... just write TypeScript and run.
We choose github actions because it was tied directly to github providing the best pull-request experience etc. We actually didn't really use github actions templating as we'd got our own stuff for that, so the only thing github actions actually had to do was start, run a few light jobs as the CI was technically run elsewhere and then report the final status.
When you've got many 100s of services managing these in actions yaml itself is no bueno. As you mentioned having the option to actually be able to run the CI/CD yourself is a must. Having to wait 5 minutes plus many commits just to test an action drains you very fast.
Granted we did end up making the CI so fast (~ 1 minute with dependency cache, ~4 minutes without), that we saw devs running their setup less and less on their personal workstations for development. Except when github actions went down... ;) We used Jenkins self-hosted before and it was far more stable, but a pain to maintain and understand.