The other incorrect assumption is that "something" would automatically convert your disk to GPT even though such a feature isn't mentioned in the documentation nor does it appear in the installer's UI.. As it happens, the only known OS/2-based MBR to GPT converter is sitting here on my hard drive. I offered it to one of AN's principals but he declined the offer because he couldn't imagine a reason someone would want such a thing. Sad but true...
If you assume, that someone would update to 5.1, i.e. on a working system, but then would have leave MBR as it is, then yes, you don't need the tool.
But I really don't want to reinstall my development machine, just to have GPT partition. On the other, hand, the only way to also have Windows 10, Linux and MacOS (!) on the T480, was to install a second flash drive just to have ArcaOS on it and have my boot manager reboot through the BIOS to have boot the MBR disk.
I would be happy to test your tool.
To finish your CSM->EFI conversion, you just need to create the EFI partition. Here's how:
* boot up yur new install using the USB strick
* open MiniLVM
* select System->Create EFI partition; follow the instructions
* select System->Boot Menu->Install/Update; follow the instructions
* eject the USB stick and reboot - you should get the AN Launcher menu (i.e. AN's EFI boot manager)
Edit: MiniLVM offers these options for a GPT disk. I _assume_ they're also available for MBR disks. If not, it's still easy to create a bootable EFI partition - you just have to copy some files.
Do you know, whether the EFI files installed via MiniLVM are the same as the ones on the USB stick?