Freerdp might actualy work as well!
Freerdp looks like a somewhat user-unfriendly RDP client, but appears very, very, very configurable and seems feature rich /feature complete. As in, there is quite a few options.
And it appears you can use it as a server as well! (Which explains freerdp as an alternative solution to xrdp.)
Also, there seems to be some kind of WebConnect / HTML5 server as well, perhaps in a way a little like Apache Guacamole.
Which means you could host the RDP server and a WebConnect / HTML5 server, all from a Manjaro ARM device (if it is all supported). And then connect from anywhere using a browser.
So, in theory that all seems nice.
Documentation however, is quite another issue.
Plenty of options and configuration, but not much accessible documentation I could find. And quite a bit of what I found seems fairly dated.
Interesting possibilities, but requires quite a bit of time to investigate.
Thanks for mentioning it 0n0w1c ! Seems like the possibilities here are bountiful.