Simply banning them clearly isn't the solution because they just keep creating infinite alts for free by watching ads so ban-evading is extremely easy. They mostly use their accounts to spam slurs, post derogatory stuff in chat, have offensive names and out mafia numbers. If they get town they just try to get themselves killed by not claiming on stand, fake claiming jailor and getting the jailor to execute them on purpose without claiming their real role, not vote with town on purpose. Even if you can just lynch them, spending your days lynching someone simply because they're throwing isn't fun and ruins the balance of the game.
The 3 most affected modes (imo) are RP, Ranked and Classic TT (that mode died because of those people).
The most obvious way to deal with this is by making the mobile version paid. Either put a paywall before people could even download the game or keep the game free to download but remove the ad tickets and only add purchase options. If that's not possible then there are other more drastic ways to deal with this that are less favorable like: being required to give your phone number; seperate steam and mobile gamers; make classic only playable mode for mobile, etc. Currently i can't think of anything else so feel free to put your own suggestions.
"Just play coven" - well yes and no. While coven doesnt really a have problem with alts, I don't think the only reason people should buy the expansion is because the base game is an unplayable cesspool. This game should have a better reputation than that considering how niche the social deduction genre is. The "Classic" coven modes aren't even playable without discord friends and not every person who likes classic/rp/ranked will enjoy coven all any.
If the devs still care about the game they need to prove it. If they really need the money from mobile ads that bad that they're willing to let trolls ruin the game can't they just try creating a patreon or launch a 3rd kickstarter if they're in such a dire need of sustaining themselves?
I can understand if they're tired of working on the same game but i hope we see more communication from them.
(feel free to comment whatever you want on this post i just hope the devs will read this themselves)