Github provides hosted runners for Actions workflows, but those are not publicly reachable as such. Build artifacts can be uploaded within Github (including as releases), but application deployments generally need to happen outside. I’ve read about services where you have the Actions runner connect to them and then can tunnel into it via that services, which may be useful for debugging (but not something I have used). But that’d still be via a third-party service.
Either way the usage limits for Github-hosted runners are probably not what you want for a manual test environment, especially the part where jobs are cancelled if they run longer than 6 hours. Another thing is that you mentioned using private repositories, which means you will be billed for job run time by the minute (with some amount included depending on you account type). Finally I’m not sure if that kind of hosting would be within the ToS on Actions Usage, but if that’s the only remaining issue you should ask Github staff about it.
In summary, I’d recommend using Github Actions for automated tests, and (if they pass) deploy to a suitable hosting service for manual testing or customer review.
I haven’t used any of the services you linked (nor any similar one), but if they do what the websites promise either of them should work for what you described.