Don't worry about the MS vs SI designation. Both are handled by the firmware.
There is a setting in the 'Expert Settings' part of the menu structure to select the MS or SI part.
The firmware files with MS or SI in their names simply have that setting initialized to the stated value.
I see that on initial load of Hugen's release page, for v1.2.27, it only shows one file for the -H4, and it has MS in its name. But if you click the link that says "show all 17 assets", it brings up the rest of the list, which includes the -H4-SI files. These would be the correct ones for you (.bin if you use STMCubeProgrammer, .dfu if you use DFuseDemo or nanovna-app).
I would still recommend, however, getting the DiSlord 1.2.40 build, at the link I previously gave, since it has new features and a few improvements, which apparently Hugen has not yet merged into his release.
Stan KC7XE
