Sometimes it's the code that is flaky and not the test.
In case of concurrent execution there are a only a few reasonably working tricks like Relacy and other exhaustive ordering checkers as well as formal proofs.
Neither is cheap to use, so you will always get flaky tests there - or rather tests that do not always fall.
if the code is flaky then I have earned my pay honestly, this is a problem that should be solved.
Subtle concurrency issues are indeed very difficult to be found debugged and reproduced and randomization could help with that simply by covering more space.
In case of concurrent execution there are a only a few reasonably working tricks like Relacy and other exhaustive ordering checkers as well as formal proofs. Neither is cheap to use, so you will always get flaky tests there - or rather tests that do not always fall.