I started this thread so I thought it appropriate that I give what I think is the answer because I did lean on quite a few people and the thread was quite extensive. In order to disable boot on z 390 ASUS motherboard on my TUF Gaming Plus Wi-Fi set one has to go to firmware> Advanced. From advanced to secure boot and change secure boot mode from UEFI to other, exit and save changes. This disables secure boot. To enable it, the reverse is done. It can be verified through either system information or Security >Device. I hope this helps someone who follows me with this issue who wishes to use some Linux distros.
Unfortunately, ASUS, and the builder did not provide the correct fix nor did any forums I tried including the ASUS forum.