I need to correct myself here: #7166 (Option to only allow signed mods for multiplayer games) by @Dunedan.

Well, it’s not as simple as it seems, since it’s very easy to pass one mod off as another. You just need to change one or two files and that’s it. 

I like that suggestion and couldn't believe there isn't already an Issue for that on Gitea—at least, I didn’t get any positive search results.

I don't use them so I unactivated them and solved, for me..

The best fix to the problem of some players using mods against players not using mods, is to make the mods currently enabled visible to everyone when a player joins the match lobby, perhaps as part of the “username joined” message. Then the host of the match can ask the new player to disable said mods. Additionaly, the ability for the host to ban certain mods, or ban mods altogether, or only allow certain mods, might be useful (of course this would take having a list of every possible mod, or at least knowing the name of the few mods you allow). Finally, maybe players can only join a match if they have the same mods as the host and as every other player, though I know that this already kind of exists, and has caused @Emacz some trouble.