Do you have any tips for how to work on this with kids?

Camps, hobbies and other such activities where they see others their age do things and have a good time. As a parent, you're not necessarily the coolest thing in the world. However their friends and peers with varied backgrounds can fill that role. I used to do youth work when I was younger and some of the biggest leaps of personality happened in groups with very mixed backgrounds. Poor kids, rich kids, sporty, dorky, introverts, extroverts and everything in between, in the right environment they'll rub off on one another in all the best ways.

Off the top of my head, I do several things:

1) tell stories of how I came to enjoy something I previously had not

2) don't make anything contentious...respect preferences while insisting they can change those preferences if they want to

3) help them gain competence quickly in anything they may not love at first

4) exposure and enthusiasm about lots of things

5) never trashing things and never ever shitting on other people's likes.

Would like to know as well. Whenever I suggest something new it's a default "NO!". But if it just happens naturally it's ok. Like if I put on a song and suggest he listen to it, my kid will literally scream and cry like I'm torturing him, but if it happens to be on the radio while driving then suddenly it's fine and he'll love it. I think part of the reason is that everything is on demand these days, unlike when we grew up on broadcast tv and radio.

Limit options. If the only, say, film options are five movies they’re resistant to watching, it’ll take very little time for them to break down and try one.

You do also have to restrict plausible substitutes, like if you do this with movies you need to either cut off or do a similar thing with video games.

Worst case, they don’t try the things you presented, but do go outside. Oh no, what a tragedy, lol.