It also doesn't have a proper web interface and Xcode is already one of my least favourite tools, so I'm not keen on the prospect of relying on it even more than I already do.
You already don't have a choice. The iOS build tooling only runs on MacOS. So your current options are:
1. Run all of your CI infra on MacOS (literal insanity)
2. Have dedicated mac minis just for building iOS apps (waste of $$$ and additional maintenance hassle)
3. Use a build cloud (somehow even more expensive than option 2)
I have not yet looked into the details, but this new Xcode Cloud free tier might be a godsend for me. GitHub Actions sucks, and their on-demand MacOS runners are crazy expensive. This will let me flip over to Xcode Cloud for Apple builds, save the $0.16/min I spend on GitHub Actions MacOS runners, and probably have a much better experience overall. The web stack gets built on GCB and deployed to GCP, and the mobile apps would get built on Xcode cloud and deployed to the App Store.
What else is there? For web things I already have some GitHub actions taking care of the work.