I left SAlt recently so I can give you an anti recommendation. Joined because even though they were trots, they seemed to have good union struggles going on and no public abuse scandals like PSL. Unfortunately,

• their meaningful campaigns (Amazon union, NALC reform effort) are national and my branch didn't want to participate in local struggle on its own.
• public abuse scandal right after I joined. I don't think national leadership responded adequately and the members didn't eject leadership
• ultimately the US section's position on the national question is wrong, and that poisons their analysis of Palestine. They think that Palestine will only be meaningfully freed with the cooperation of Israeli working class. IMO this leads to reprehensible policy positions which prevent them from meaningfully interfacing w the antiwar movement

If you have multiple orgs in your area, you can always just join for a couple months and investigate for yourself. Even though my time in SAlt didn't improve the world, I still got much better at talking to people about socialism irl, and working through my disagreements with them sharpened me politically. I think the reason the US left is so fucked up and weak is that the working class in general isn't organized, and a strong left movement grows out of mass class consciousness. There were plenty of social democratic orgs all over pre-revolutionary Russia; where there was no worker struggle they withered away and where there was worker struggle they thrived. When you talk to socialists, the difference between organizers with union experience and activists without it is palpable. With historically low unionization it's a question of what is the least-bad org to join.