Then I don't understand what your issue is. > We had a few "releases" which needed very urgent hot-fixes because of last-minute changes and not enough testing

Then I don't understand what your issue is. > We had a few "releases" which needed very urgent hot-fixes because of last-minute changes and not enough testing on hardware. That sounds like the problem is that the CI is not testing on hardware, or that you're running ad-hoc manual tests on hardware that could be automated or at least formalized.