I’m a bit unclear on all this too, so I’ve chosen to use team 1 as the lobby team, but suffer from no team 1 in the scoreboard.
What I can say so far is…
I suspect Play mode may interfere with initial spawning since there is no pregame phase in testing.
Teams must be set to Dynamic in Island settings, otherwise the engine takes over team assignment and does what it wants.
I remember in a post way back, someone set thier island start spawnpads to the team they wanted and that worked, I think they tried a class selector zone covering all start spawns first, but that was before it had an overhaul that came to include send team changes at warmup.
Was also having trouble at some stage because the team would not change without a respawn, but I see lately from others projects, that teams are changing without a respawn by going through a teleport, but I can’t be sure and haven’t tested it.
How did you try the team assignment ? Was it a class selector change player to team from the player spawned event ?