I've added a link on the MOTD to the custom campaigns which are installed on the current server.
Example for alServ2019:
Press "H" or type "motd" to open the "Message of the day" page.
You will see that
[You must be registered and logged in to see this link.]Then you will see all clickable links written underlined in green font.
Click "custom campaigns" there to open the well known
[You must be registered and logged in to see this link.] right inside the games MOTD panel.
In the list you can sort by clicking in the header of the columns.
You can also click "show banners" to display the gamemaps banners (maybe helps to recognize the campaigns more easily)
or you can click the campaign name to open the whole gamemaps.com page.
To get back to the MOTD page, close the motd and open it again.
This may help to search and select a custom campaign to play without leaving the game.
Then use !votemap and select the campaign in the list.