Surface Go 2 -unable to install

Hi,
I’ve problems to install FydeOS as Multiboot OS on my Surface Go 2.
I disabled secure boot, changed the boot order, so that “USB Storage” is first, the secondary is “Internal Storage”, and after that “Network V4”, followed by “Windows Boot Manager”.
As install media I created a USB Stick with the actual 20.0 image, and of course I shinked the Windows C: partition by 100GB, and created a new partition without assigning a lettr, so that it is displayed as RAW partition.
It starts from USB, and I’m able to start the desktop environment with google login.So far so good. But I’m unable to install it! I can start the installer from USB or from the desktop after install it from the app shop. I select the 100GB partition, also the EFI partition (nvme disk), and tried the recommended “rEFInd” and the “Multiboot Manager Installation”. Then it starts without any errors, all steps seem to be OK, I get the message to restart the device after install media took out -and after reboot it just starts Windows, and if I look into the Disk Management, the 100GB partition is still RAW.
2 thoughts I want to share: to reenable “Secure boot” makes no sense, or? And: the RAW partition is not the last on the disk -after that 2 Windows partitions, ~1GB each, for rescue follow -will this make problems? May the first one, EFI-systempartition, is with 260MB not big enough?

Did anyone have a glue or suggestion?
Best regards
John