CloudReady v61 and Ubunut 18.04 boot issue with kernels based on v4.14 or above. If the HP dc5800 BIOS version is lower than v01.53 the systems will not boot.

The minimum version for these systems to work is v01.60 which can be downloaded from HP. This will need to be updated for compatabilty.

https://support.hp.com/us-en/drivers/selfservice/hp-compaq-dc5800-small-form-factor-pc/3658082

https://neverware.zendesk.com/hc/en-us/articles/360000302447-Updating-BIOS-on-HP-Compaq-dc5800-

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1772038