Hi,
With our pre-configuration of WebUI DMVPN requiring IPSec, you will not be able to exclude it, so you will have to configure DMVPN through the console and third-party package.
Third-party packages and other custom apps are not in our development reach, so use them at your own risk.
Also, you might also look for possible no IPSec configurations in OpenWRT forums, there should be people also having the same idea of removing the encryption of IPSec.
EB.