AMP works..
Just to chime in that I have implemented AMP pages on several of my own sites (not Xenforo, but custom-built ones), and have seen mobile traffic go up and rank better without having to put any extra effort in.
One of my sites currently has 70 users online, 20 of those (28.5%) are visiting an AMP page.
- For the past week 55,531 sessions of which 15,591 were AMP ~28%
It will definitely help you rank if the content is relevant
Having a page that loads almost instantly (super well cached) is something that is very much preferred for a user on mobile.
And if you think that Google doesn't care about optimizing the user experience for their users, think again
AMP as a landing page
The point raised about thinking of it more as a "landing page" is very valid.
One of my sites is a one-page webtool, and the AMP variant of it doesn't work (due to being reliant on custom JS), but it still has very relevant content. If the user wants to run the tool, it's simply a matter of clicking on the "
Run tool"-link that points to the non-AMP variant, which will be able to execute the custom JS.
Personal preference
I myself almost always prefer the

-links in search results, because I know I will see the info instantly, and I won't be bogged down with 3+Mb of unnecessary JavaScript.
Someone make a plugin for this already!
@Recep Baltaş where is your SEO2 plugin? did it have AMP support? I'm asking because
@NixFifty hasn't released the AMP plugin for XF2 yet (and doesn't seem to be too active)
Seriously there is $$ in it for you, as anyone who cares about bringing traffic to their forum can install it and rank better for various things. Paying a couple $ for a plugin like that is a no-brainer!