I went down this rabbit hole yesterday. I documented the steps used to create a Adguard Home container in Vyos 1.4:
I went a little further and used the Vyos forwarder listening on a different port as a recursive DNS server that Adguard uses to avoid using public DNS servers but that’s not reflected in this guide. Adguard not supporting this out of the box is a little silly but there are workarounds.