Unless it boots from a floppy image - then it goes into MSX-DOS.
I think. It's been a very long time.
CP/M or so, the father of DOS
They should be able to boot into CP/M. Even MP/M should be possible.
You need to provide the firmware, because they aren't free to distribute. There's an open source one, but it doesn't boot to BASIC and can only be used to run cartridges.
And it is because is not an MSX, it emulates one with an FPGA.
Thats a boomer. So no real MSX, but sorta kinda MSX inspired…
You can find all roms easily though and then indeed boot into basic.