I highly doubt it.
Regardless of the packaging (Chateau, SXT, WAP) the restriction will be on the modem used on the inside I think, the Chateau LTE has had a new refresh in 2023 and it now sports a new Modem (FG621-EA)
There are already a few new Mikrotik devices that use that new CAT6 modem (I have deployed a few of the SXT ones with that radio) and I also tried putting a MTN fixed LTE sim in, and initially it worked well for a few hours and then it was blocked.
I think the reason why the original LTE6 Mikrotik's weren't allowed (Modem : R11e) was because they could not do CA with band 1 + 3 which is where you get some of the best speeds on MTN's network.
Which is probably why the Chateau LTE12 as approved since it can do CA on those bands (It even supports 3CA with band 1 + 3 + 8) which MTN can do.
@Afrigirl If you ask MTN to specifically test any new Mikrotik with a FG621-EA modem and they are happy they will instantly be able to add like 4 more devices to the approved devices list.
Like I said, it's a new CAT6 modem that supports B1+B3 aggregation
Many users like myself want to install LTE as a backup WAN, I don't want to buy some consumer grade router with built in WiFi or crappy firmware (or inferior antennas that require me to add external antennas)