Note that Qubes-4.2.202308270121-x86_64.iso forward should include the fix to use fedora templates for dispm sys-net.
Haven’t had the chance to fix it myself, but should be there. This iso+detached signature should boot from Heads.
Note the recent builds of Heads now support exfat by default. This means that if you bought a SD card or a USB thumb drive, you can download iso + iso.asc directly to that drive and boot from USB from Heads to test it directly without having to verify either integrity or authenticity of the ISO. Heads will take care of it (tested in prior weekly iso.)