Preempt_rt options / Thoughts on usage of mainline?

Hello

I’m looking into using a kernel with the preempt_rt patch on an Altera Cyclone V. I’m considering the different alternatives for achieving this, and I wonder if anyone could provide any inputs or clarifications.

At some point the Altera fork was released with the rt patch regularly, but as far as I can tell, this has not happened since 2019, where this seems to be the latest released version:
rel_socfpga-4.14.126-ltsi-rt_19.11.03_pr

Does anyone know whether or not this is correct?

Another alternative is to try to match up an Altera fork lts release with a preempt_rt patch release. However, the latest Altera fork lts release (6.1.20), has no corresponding preempt_rt patch, so I would be forced to either try patch 6.1.12 or patch 6.1.26. If they prove to be incompatible for some reason, I would have to either resolve it, or go back and find the latest releases where they both match up I guess.

Last alternative, but in my mind the most desirable, would be to use a patched mainline kernel, for instance the v6.1.46-rt13 from linux-stable-rt. I have it running on the board, and everything is seemingly working. However I’m unsure as to whether I will meet any issues down the road by using a mainline kernel.

Any inputs, tips or thoughts on this issue would be greatly appreciated.