I am new here. But this is a very IMPORTANT issue as booting on various configurations of 64bit PCs over the past decade is in constant flux at both the POST levels and drive devices.
BUT, one Linux seems to have addressed it in a satisfactory level…at least for now.
PREFACE: Their solution, which is applicable on this thread’s for your ISOs, is addressed for hybrid ISOs. Yet it is adaptable here to support Clear Linux.
Puppy Linux’s GITHUB (there are multiple entries on their GIT) has created a solution that will boot on BIOS PC, EFI PCs, 32bit UEFI PCs, and 64bit UEFI PCs with a single boot process image. Further any ISOs that are created using their technique since beginning of this year will ALSO boot their ISO, natively, without ever burning the ISO to either USBs or DVDs or drive media by using a Linux boot helper named SuperGRUB2Disk. SG2D has a GITHUB coverage as well.
You might do yourself a favor to reduce sleepless nights by reviewing or appealing to their work. AND if ClearLinux ever produces a hybrid ISO, their technique will work as well there to allow a live boot to ram via SG2D, simply and natively without disturbing the system disk contents.
Shorten your work effort and take the experience via GIT SG2D’s work for booting ISOs without burning to media as well as booting all types of PCs that GIT Puppy Linux has demonstrated.
Hope this reduces your workload and allow sleep with peaceful knowledge.
P.S. Puppy folks are very responsive while SG2D is a little/lot less so.