Something you can just easily play with friends, on the road, and with rules that are as simple and clear as possible.

Maybe you should just google some list of card games, the most popular and simple ones? That’s exactly where the rules will be. There are a lot of them. Explaining each one would take a ton of time.

I haven’t played card games in person for ages, just with friends and with real cards. Mostly, it’s something online, for example, Spades-Game, but I think you should check out the rules of that card game. I think you can totally play it in person. Just that the rules are really simple and clear, and even someone who doesn’t play cards will get it.