How do people get all their chat apps into one window on a laptop?

This is exactly what unified inbox apps are for. Spanbox runs each of those as a real tab inside one window with a single combined unread list, and it is local-first so your accounts stay on your machine. Beeper is the other name people mention. Either beats ten browser tabs.

Worth checking your notification settings too, they quietly reset after big updates.

Restarting the phone entirely did it for me when nothing else worked.

Two routes: a wrapper app that holds them all (Spanbox, Franz, Rambox) so it is one window, or discipline with a browser profile just for chat. The wrapper is what stuck for me, one shortcut jumps between all of them.