How do I boot a linux distribution from a gpt usb drive

Question

I can for example have Gparted on a thumb drive and it boots fine.

I can make a gpt drive on an external usb drive, have several partitions and have several

different winpe or winre distributions and they boot fine.

But if one of the partitions has a linux distro then this happens:

Could not create MokListRT: Volume Full

Could not create MokListXRT: Volume Full

Could not create MokListTrustRT: Volume Full

Something has gone seriously wrong: import_mok_state() failed: Volume Full

The winpe / re still boot.

But the same distro on a thumb drive boots.

Any idea why this happens? Even if secure boot is on or off same errors.

And all is formatted fat32. Thanks.