Teensy 4.1 + LinuxCNC

You could also test its performance over a simple ethernet switch. Its not really recommended but mesa cards can work over them so that would be a nice feature to have in this. The latency certainly has some headroom for it.

any new on how this is progressing?

I bought one of Teensy 4.1 grblHAL breakout board back in the summer and I'm keen to know if I'll be able to repurpose it to use with linuxcnc.

Thanks for expressing the interest.
I know Phil's board - it is a good layout.
As my code is relying on hardware and I would like to keep the possibilities to read encoders for closed loop control, I don't think my implementation will be pin compatible to Phil's board, but I have to check this in detail in the upcoming weeks.
Anyhow, I plan to design my own board once the pinout is fixed.

At the moment, I am still working on the module for stepper motor.
To avoid interrupts and to keep down the latency I would like to count steps in an efficient way with hardware counters, but I still have some difficulties. I hope this will be ready by Christmas.

In future, I am looking forward to use distributed clock using PTP protocol. Any expert on the topic around here?

Have you made any further progress on this? Is the code available anywhere online?

Thanks!