Since I've just found out that you have never tested the M44 board that I have, I was wondering the same thing about the 5441?
Have you tested one with the UC300ETH, and does everything work properly?
The 5441 seems to have all of the features that I want, but it is rather expensive.
I'm not sure how to go about purchasing one, though, as I can't read their website.
https://www.cncpart.hu/uc300-5441
I'm not interested in purchasing at this time, but if I do later, I'll contact them.