Sounds a bit like my partner, who doesn’t like most action games. For a game you could play together, I think you could try a “creature collector” type game, like pokemon. There are actually a lot of creature collectors, pokemon is just the most popular, but there are cheap digital games on the switch store that are made by Pokemon fans and from what I can tell are better in a lot of ways.
You can also emulate all of the old console games for free, that’s what my partner did for a bunch of Pokemon titles.
I also recommend this game as one of the best co-op / split screen games I’ve played.