hangs at “booting…”

On some serial connected devices the console settings are different, in which case you would not be able to start the installer.

If you can reach the loader prompt, you could try to change some kernel parameters before booting.

set hint.uart.0.flags=0x0
set hint.uart.1.flags=0x10
set comconsole_speed=115200
set comconsole_port=0x2F8
set console=comconsole


To enter the loader prompt press 3 when the OPNsense boot menu is visible

After installation, you could persist these settings in System ‣ Settings ‣ Tunables