I’m gonna say Spirit Island is a solid game that is also co-op. There is a solo play as well, and the app gives you a small taste of the game without any purchase. (It’s limited to like 3-4 rounds of play, a taste)

Daybreak and the Slay the Spire-boardgame edition are both cooperative and plenty of fun.

This is an old one, but an extremely good one: The Lord of the Rings (from 2000). I’ve found that it works pretty well with as few as 2 players, but even better with more. It’s not impossible to find. There are people on the Board Game Geek market selling it for reasonable prices.

Dorfromantik: this is co-op tile placement game, with some interesting strategy. With each new game, you’ll unlock additional tiles that will let you score more points for the next time. This won Spiel des Jahres in 2023.

Camel Up: while not exactly a co-op, players place bets on a camel race. It’s a fun party-ish game that feels more like the board against the players.

Any of the Zombicide games (including Massive Darkness): these games are lighter dungeon crawler type of a board game. While there’s some strategy, it’s mostly about killing enemies, rolling dice, and getting loot.

Gloomhaven: a deck building, dungeon crawler, this game is much more complex than Zombicide. It’s rated #4 on BBG. Be ready for a long set up, though!

Kingdom Death: Monster: I have never gotten this game to the table, but it’s a boss battle, dice rolling, campaign kind of game, where you can loot the bosses and craft gear.