Can the OPI5 be Configured to Run LCNC?

Yes, see: forum.linuxcnc.org/18-computer/48079-can...cnc?start=200#273554

also with spi connection to mesa card like rpi4 ?

I don't know if there is a SPI driver like the RPi from Linuxcnc (this is a dedicated driver for only the Rpi3/34), as per the RPI the /dev/spidev driver probably wont give you the speed you are after.

Unless you already have a 7c80 or 7c81 I'd tend to stay away from the SBC's and go for a small form factor x86 system (if space is a concern) and an ethernet mesa card. That way you wont be stuck when you need to update\replace the computer. Ethernet is everywhere, SPI seems to be the realm of the non-x86 platforms, and each SBC will require it's own driver, which requires someone to develop & maintain it and you are at the whim of the manufacturers\dealers regarding availability........and the infinite number of models.

Another thing to take into account some of these SBC's require messing about with the uboot loader, or whatever flavour of boot loader is used, to use a realtime kernel.

They have their place, it just depends how much time you are willing to spend and whether it will be obsolete in a couple of months to a year.

This seems very good for use with mesa ethernet card + extra ethernet for internet
www.hardkernel.com/shop/odroid-h4-plus/

@cornholio not a single one here that had to mess with their ubootloader.
To build a rt kernel is also pretty easy or just download and install. Mainline Linux support is getting there too, it's already usable.

@vre There isn't a SPI driver like on the Raspberry Pi indeed but a /dev/spidev like cornholio said. If I can test the speed with a microcontroller or something I'd like to test it.
@cornholio Is there a reason that this can't work fast enough or just a guess?

Mesa over Ethernet might be the most safe option. An Opi5-plus has dual Ethernet too.

Regarding uboot first post of the thread, so you're saying this has changed now ?
forum.linuxcnc.org/18-computer/48079-can...-lcnc?start=0#263021

Regarding spidev
linuxcnc.org/docs/stable/html/man/man9/hm2_spi.9.html

I've tried it and it just doesn't work on the Rpi5, using 7c81 firmware on a Xilinx dev board (which has the same FPGA as the 7c81 and there's no hardware issues, SPI cable is well grounded & shielded and only about 2" long). The hm2_rpspi driver actually unloads the kernel module, the Linuxcnc driver is actually a direct acting driver on the Rpi3/4 spi hardware. The spidev kernel driver has has to call to the underlying driver that talks to the hardware (and these drivers in themselves may not be optimum for RT cnc work.).

You can load the the hm2_spi driver from within halcmd and everything works as should, but once you start adding the read\write to the servo thread errors start happening. I haven't tried increasing the servo thread as I didn't think is was worth it.

Now I'm using the same hardware with the EPP interface (x86 board), runs fine no issues and talks to Smart Serial boards without an issue.

Regarding the uboot, that didn't change, hoping that it was good enough did the trick.

It looks indeed that the chance is small that the SPI driver will be fast enough, still worth a shot, but better not to count on it.
Pinning the irq of the spi to the isolated CPU might help by the way.