Can the OPI5 be Configured to Run LCNC?

I was thinking, when I ran my long latency test, I got some strange outlier interrupts when I did it with youtube running in the background. Youtube would have been running over the internet.

I'm thinking it worthwhile to bring the machine back in (not internet access in the workshop) to rerun the test with Youtube and the IRQ affinity set.

I've seen that too while playing a yt video in the background. It looked like the video froze while it was out of sight and filling up the memory, the moment I made the window active it catched up and that seemed to cause the latency.

If you had the same issue I don't expect that the IRQ affinity will help. Playing yt works fine as long as you pause the video before you bring it to the background. Perhaps the newer kernel or updating mpp will fix it.

I had to bring the Control Box back in for some rework anyway, so I put it back to the latency test for an overnight run.  isolcpus=4,5,6,7 and "f0" in the smp_affinity.  Six glxgears, and a browser playing YouTube videos.  Left it running all night and all day.
The previous large outliers are gone, so I think I can safely rely on 15us for latency, with the correct IRQ correction command in rc.local

Also, even with all the large cores dedicated to the rt threads, the UI was still plenty responsive.
Also again, @royka 4,5,6,7 worked much better than 2,4,5,6

I added the affinity commands to /etc/rc.local, but they aren't getting picked up.

Fixed it.

Put "sleep 10" on a line before the echo commands. It appears that /proc hasn't been created by the time rc.local gets run. sleeping for 10 seconds gives it time, and I can't log in that fast anyhow.

rc.local is obsolete. Have a look at this article which describes how to use rc.loacal and also how to do it with system.d which should avoid the need to sleep

linuxhint.com/use-etc-rc-local-boot/

Yeah. I looked at that. No thanks.

I'm not prone to using a jack hammer to drive brad nails.

Tonight the job is to figure out why my encoders don't work. I got a hunch last night that is is because I'm using wire that is too thin.

It's there and works. Just had to add a short pause so that /proc could be created before writing to the files there.