You should be able to enroll the Secure Boot key for Bazzite and keep it enabled. Instructions: https://docs.bazzite.gg/General/Installation_Guide/secure_boot/

Did you upgrade to the latest bios version?

Factory reset the bios?

Check for option pins on the motherboard?

How did brazzite install with secure boot turned on?

Could have been disabled by the vendor. My partner has an Acer with the same issue.

On some BIOSes you have to set and enable master password for some advanced options to show up.

in some its called other os like on rog ausus boards could be same or its alienware so the bios may be more restrictive

Secure Boot settings should be under the Security tab in the BIOS.