It probably is a decidedly nonstandard setup but I literally use plain Debian/unstable even with the CUDA libraries from the non-free section of their archive (they just don’t have cudnn so I take that from NVidia). The other day profiling with kineto would not work but other than that it usually just works and use cmake, python3-dev python3-typing-extensions python3-numpy-dev python3-yaml and so from Debian. No conda, docker or other funny business.   But again, this isn’t the standard way and maybe someone else would have better advice.
Unless you need Magma for what you are changing, you could just compile without. USE_MAGMA=OFF or so.
You can also just start the tests by running test/test_something.py TestCase.test_me or use pytest with -k to filter.
If it’s a targeted fix and you have a test case for it and are reasonably sure that it works, you could probably just open a PR for it. I wouldn’t debug code with the CI, but I have certainly submitted patches where I had overlooked failing CI cases because I ran tests locally to narrowly. So far no-one bit my head off for it for that. 
git-clang-format and python3 -mflake8 are probably a good idea to get right on the first submission.
Best regards
Thomas