Whenever a bootable OS install image is put on a usb thumb drive, the BIOS mode on the thumb drive will be configured with the same BIOS mode as the PC that is used to create the thumb drive. The two options are Legacy Mode and UEFI mode. Once an OS is installed on the computer device, in a given mode, then the BIOS cannot be changed to the other mode – i.e. the computer device will not boot in the other mode. Please note that older PCs and servers only support the Legacy mode.
Here is a good link that discusses the Legacy and UEFI modes.
https://www.onlogic.com/company/io-hub/uefi-vs-bios-building-a-better-firmware
All of our current Dell 3070 and 3080 PCs are configured with the UEFI mode from the factory (including WS91 and WS92).
All of our HP BL460Gen8 server are configured in the Legacy mode.
I recommend that you check all of your bootable USB thumb drives and label them with the BIOS mode (Legacy or UEFI).
https://www.nextofwindows.com/is-my-bootable-usb-drive-uefi-bootable
Example: I have some Windows 2016 Server bootable thumb drives. Some are in Legacy mode and some are in the UEFI mode.