Had this issue with a J4105 Gemini Lake part. Perhaps it's the same as the X55's J5005 Gemini Lake part?
http://rob.com/porteus/ProxmoxH2.iso is a 642Meg Proxmox VE 5.3 install image that works on the Gemini Lake and Coffee Lake systems I own in uEFI mode. It boots and runs normally, but...