Some people do say NTFS works. I reckon a USB works as well but didn't want to contradict Walone. I do my speed camera updates on USB as well as SD. USB is fine, I reckon I've read people doing it that way although given can drive about during the update, SD should give you better contact than a pen drive.
Walone is your man for firmware updates. He updated his prior to getting it modded although I don't think he has an H50 unit. Mine is H50, was software 0674,
Ateca 2016. So we both used the same small company to get are Mib2 Highs turned into retrofits but had different units.
Mine was:
5F0035020C
0674
After the mod it went onto
5F0035020G
1338
There is a thread on the board
https://forums.seatcupra.net/index.php?threads/sw-update-for-mib2-infotainment-system.427280/page-20
They use the Spanish site mentioned in that thread but they aren't modded ones just the standard release. Your current part number 5F0035020B was the one before mine. So 5F0035020G will be fitted to some Seats. When I looked in December I couldn't find the release that I'd been put on. I was just trying to track down whether that original release was in the public domain. I never found it. You have to go threw the Spanish thread looking for H50... Well that's what I reckon. The company we used turned me away the year before but could do it a year latter, that I believe was due to them being able to source the H50 firmware. So that was my check, you might have better luck, failing that you'll be looking for a specialist.
I pass on the rest over to Walone who did do a firmware update but not on an H50.