I've just tested this on Mobian Sid on PinePhone. Selinux still doesn't
seem to be configured by default with `selinux-basics` and
`selinux-policy-default` installed.
Placing the below file in /usr/share/u-boot-menu/conf.d/zz-selinux.conf
resolves the problem. Note the `zz-` prefix or one like it is mandatory
as this must be processed after the Mobian config which will always
overwrite the `U_BOOT_PARAMETERS` variable.
```
U_BOOT_PARAMETERS="${U_BOOT_PARAMETERS} selinux=1 security=selinux"
```
Thanks.
