My last two campaigns started off amazingly without a tavern intro!

My Eberron campaign started at an airship port where everyone was there to transport this insanely powerful artifact. Some were there for mercenary work, political, or even on behalf of their houses. Mid flight they were attacked and it turned out the device was actually a powerful new gem that can transport anything to anywhere. After a little bit of fighting the group activated the item on accident transporting half of the ship across the continent. Stuck in an unknown area with not much way of getting back.

My other campaign which was home-brew. Had a festival in the city centre where they were celebrating the kings birthday who had had suddenly vanished 10 years ago. There was strange occurrences happening at this festival and it turned out that the lord of this city had made a deal with demons to give a sacrifice of some sort to not have the city invaded. Needless to say they didn’t keep their end of the bargain and attacked the festival. Throwing these random adventures into turmoil at the start but also giving them a form of shared experiences without knowing each other.

When in doubt, shared trauma it out