Its broken in the sense that it doesn't work, but it isn't broken in the sense of oops we accidentally broke something.
They added BattleEye anti-cheat to online, without bothering to support linux.
Even though BattleEye can and does support Proton compatibility, and has for years, the developers of the game have to request or opt-in to this functionality.
But uh, Rockstar didn't, because they don't give a shit about linux players.