There is still a lively academic community and major progress! Check out CMU's no limit results [1]. (I realize articles like this have to pick some angles to make it interesting, but it was weird to see only dated research mentioned.)
But if you are rooting against the machines, don't worry: it is almost certainly impossible to calculate a full equilibrium policy for no limit multiplayer, so we will instead be debating over the virtues of various types of imperfection for a long time. And even if an Oracle gave us convenient access to equilibrium strategy, it would still not be the optimum at a table full of imperfect players. Your poker game is safe for a while!
It doesn't even matter if you can calculate multiplayer equilibrium. It's not the solution the same way it is in heads-up. You can still lose if you employ the equilibrium in multiplayer unlike in HU.
That's not true in practice for poker. Pluribus showed that if you run CFR in multiplayer poker you get a solution that works great in practice. Multiple equilibria are certainly a theoretical issue for many games, but poker conveniently isn't one of them.
It's not about multiple equilibria but about (often unintended) collusion.
Examples of that affecting poker games are very well known. One frequently occurring example was discussed in online community 15-20 years ago (BTN raises in a limit Holdem game, SB calls too much which hurts both the SB and the button giving equity to BB).
I don't think you're correct saying it doesn't affect poker as people were able to notice and analyze this before solvers. It's true though that no-limit Holdem as played today (two blinds,no ante,deep stacks) is likely not strongly affected by the phenomena. I don't agree Pluribus experiment shows much when it comes up practical play. Not enough variety of skill levels, not enough hands and not enough time for metagame (people adjusting to how others play) to develop. I do agree pure equilibrium play is most likely not terrible in cash game nlhe but definitely not in poker in general.
But if you are rooting against the machines, don't worry: it is almost certainly impossible to calculate a full equilibrium policy for no limit multiplayer, so we will instead be debating over the virtues of various types of imperfection for a long time. And even if an Oracle gave us convenient access to equilibrium strategy, it would still not be the optimum at a table full of imperfect players. Your poker game is safe for a while!
[1] https://www.nature.com/articles/d41586-019-02156-9