Can the OPI5 be Configured to Run LCNC?

Yes Royka, thanks, I know more or less these things, I will try to install TigerVnc, I think it's ok.. but without fixing modules was impossible.
The broken link is inside /usr/lib/ you can find "modules" that is broken link, pointing to "/boot/lib" but boot partition is localized inside "media" because recognized as external drive (strange).
About USB I was trying to use a standard USB key, not working, not recognized at all without fixing modules.
Finally I solved deleting the wrong link "modules" inside /usr/lib and I copied and pasted whole modules folder from media/.. /boot/lib/modules inside usr/lib and now the error at boot disappears and also I have the possibility to install something.

About HAL configuration.. are you using ARISC driver for GPIO? 
I have my configuration working with RPI4 but I imagine the same driver would not work.. right?
I will try next days.
 

As I said, adding that line in my previous message to /etc/fstab would mount the boot partition at /boot, to be sure you could type blkid to check the uuid, then the link would have been correct. What you've done also works at the moment, but when the initramfs needs to be updated, possibly it makes a new file in /boot which will not be in use.

Again TigerVNC won't work in Wayland.
You could try to follow the instructions from:
discussion.fedoraproject.org/t/how-to-st...ession-wayland/78971

I don't use the opi5 at all for LinuxCNC and I've got a mesa board over ethernet. I was just curious if it would work, I might use it later.
The arisc module could work, personally I wouldn't use the gpio pins without something like a CNC shield/hat to protect the pins and most sensors/steppers needs 5v, the gpio pins are 3.3v. But that's the same as with the RPI4 so perhaps you already own one?

After reading about the arisc module, this is using the internal mcu, so I think this has to be ported to make it work with the opi5.

You are right, with the additional line you posted the issue is fixed.
I will play around the GPIO driver because I want to replicate what I did for my RPI where I created a PCB  transforming signals, inut/output and also Modbus. So I should also to find a way to use the serial from OPI5. The way still long... 
When I have something that make sense (as HAL) I will share.
For VNC I'm not able to find a solution, I read a lot about gnome-remote-desktop but all places explains to configure thought setup, but it's not visible.. not urgent, now I try with Samba, it's more helpful to pass ISO G files with shared folder but I already did in the past.. then I have to configure 7" display, I found some hints on the web... 
 

Yes somehow the gnome-remote-desktop is broken on that ubuntu version.
I've just compiled the rt kernel, which I'd tried before, but this time with the config of the existing build and enabled the panfork drm and disabled another option which is necessary to use panfork. Till now it seems to do good, but I've not tested the latency yet, I'll do this weekend.

If the latency is still as good, it means we will have hardware acceleration and have the ability to enable wifi drivers, remote desktop etc.

A quick test, without full hw video decoding yet, but 1080p does work fine.
Or the results are really this good or if hung, although the timer still worked. Need to do some more testing.

I will be very interested if it is viable. I've been mucking around with the build you gave me, and realized not having wifi will be somewhat of a problem. I tried getting one of my Netgear rtl8192cu usb dongles to work, I tried adding a PPA that maintains most realtek drivers, however when I tried to add the driver via the synaptic package manager or command line, I get an error. At first I though it might be because the drivers are built using dkms mode and Arm64 just doesn't like that, however reading that this build just doesn't have wifi. I guess that would explain part of my problem. I'd like to be able to use a usb wifi dongle so I can free up the ethernet port my Mesa board and still have internet access. Maybe this new build could make that happen.
Cheers!