I spent like 4 hours a day on Twitter before the screen time app. Now I’m almost never on it.

Time-lock using pi-hole or another interceptor? Theoretically you could put this upstream of your devices on the network in your home. Then device doesn't matter (unless you switch to data on your phone).

Part of this is not having something else to do in place of doing the old habit. Part of this is not getting a reward for doing the something else. Maybe make a list of things you (used to) enjoy and keep it somewhere visible, revisit it frequently, especially when you are about to hit a cue that sends you into an activity you want to avoid.

You can just block sites in your hosts file :)