Seems to be an issue with the Steam browser. It's been that way for a while.
I wrote up a workaround in TF2. It rewrites VGUI message URLs so they all get sent to a page that opens it up in an
iframe element. Just download,
compile, and install.
I'm not sure if Empires handles MOTDs the same way TF2 does (I recall CS:GO using protobufs and requiring pop-ups or something), but you're welcome to give it a shot.
Note that this workaround doesn't work on sites that block from being loaded through
iframes. The Steam group page is one of them, though profile pages do go through. If you have a
/group command or similar, just make sure you're sending the GID-style URL (or change the regular expression that determines whether or not a URL is bypassed).
Also, the workaround requires a static page, defined as
MOTD_PROXY_URL in the source. I'm hosting a copy of the page myself, but instead of relying on my goodwill (I lose access to the domain / my VPS box / broke my nginx config / decided to scum up the page with advertisements), the HTML is available if you'd like to host it on a separate domain; just change the constant and build. The plugin uses location hashes, so any URLs you send aren't transmitted to my server.
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