Yeah seems just like custom rule set games for BF2042, but its NOT custom servers like in BF4. Its still run by EA, you can just temporarily host games on them. From the FAQ
Battlefield 2042 Frequently Asked Questions – Learn about modes, maps, weapons, and more
www.ea.com
Will there be Community Servers?
In
Battlefield Portal, players will be able to host servers where they can run custom games or use preset modes, like Conquest, Team Deathmatch, Rush, and other fan-favorites available at launch. These servers are created when you make a match and then shut down once the server is empty.
Probably the most popular - like 64 v 64 knives vs defibs or zero planes vs F35s - will be in perma rotation and rules that people make that prove very popular will be perma'd, but end of the day its still DICE servers with custom rule sets and no real admins other than DICE/EA.
Still all the same problems of cheating, bots, cross play, etc. I have the game preordered on PS5 so will probably have cross play off so I can play in peace.
It also all sounds like its part of BF2042, while the maps from previous games will be in place you can't just run it from another game or whatever, and its not f2p. You must own BF2042 to run this stuff.
Open beta is in September so still a bit away