Hi, thanks for that correction. Do you have a keyword or 2 to google for "They can be modified, though not necessarily in a typical way." Or is that only or the CM, and not the normal RPI4?

I only found some quick&dirty patch, that seems to make MTU up to 2000 functional. But since the patch aims for 9018, and only gets 2000, that does not seem like the "right" solution.

You can do it if you compile in a kernel patch on the regular Pi 4, I believe: https://www.jeffgeerling.com/blog/2020/setting-9000-mtu-jumb...