Installed Qubes on secondary SSD; boots into first drive

i one had a somewhat similar issue… -years a go an not exactly so…
but the issue i had was a corrupt “broken” mbr
which basically go ignored by the uefi/bios
would work if “forced” but whenever there was another gpt drive th system will just automaticlly boot the gpt drive

soled this by completly repartitioning and repairing the mbr
was a bit of a pain in the ass for a number of reasons… ()first it was a pretty big drive and i had to backup everything -and well had other issues corruption did no only effect mbr but… -let me tel u somthing the software called testdisk is great for data recovery but horrificlly slow)

anyway way
check how you’re drive’s partitioned maybe that’s the cause/related

also try using another disk usually when the isue is with the component instead of system/ what’s installed on the component using a different one will reveal where the problem is
if u tried different drive etc then the issue is probably somewhere else such as in your bios