Cannot boot Mac Mini A1347 from USB Drive

I have tried every recovery and specify startup disk option that I can find for this 10 year old Intel Mac Mini. The bootable USB drive is definitely working, but the Mac Mini won't boot it. I see no errors, but it never boots from the USB drive.

Since the Mini is past EOL, I have installed Linux on it in the past, but now I cannot install anything on the Mac Mini. It still boots the Linux I installed 2 years ago, but I need to do a fresh Linux installation.

Any suggestions beyond the usual ones I've already tried?

Thanks in advance.