Gitlab and Github have pages and pages going over the domain language used to configure the job triggers. Jobs can trigger other jobs either in response to completion or as a dependency etc etc.
I would say these radicle-ci designs as they are now are actually quite rudimentary. That's perfectly fine for an early project but at this point I think you have to say that they won't have a CI system ready for quite some time.
Feels like using a free Jenkins gets you everything you want. Doesn't need more than a container or Java either.
[1] - https://radicle.network/nodes/index.radicle.garden/rad%3Az3G... , [2] - https://ambient.liw.fi/