We support GDB remote debugging, so we should be able use OpenOCD's support as a remote GDB debug target. We know from customer reports that this can work with some embedded systems debuggers, but some customers have run into problems with our startup sequence being incompatible with some initialization needed to get the program uploaded on the remote target. Haven't dealt with OpenOCD specifically, so we can't say for sure it will work without problems.
I'll take a look at CMake 3.20.3 this afternoon. Usually it's straightforward to update our support for CMake updates, but I'm not up to date on what changes have gone in CMake since the last builds.