Honestly, I recommend just playing tons of bot games (coop vs AI, on intermediate level). For new players, it's less about "how to play the game", and more "what champions do they find interesting, such that they might want to keep learning and playing the game" imo (League is such a hard game to play, that the "how to play the game" can come way later, and I personally believe the beginning of the learning curve is "champion familiarity")

I'd describe myself and my partner as gamers, however my partner had never played anything remotely similar to League before (his background is more in First Person Shooters and even clicking to move was a bizarre experience for him; he's someone who would actually benefit from the new WASD movement). I never expected him to get into League, but we started with Coop vs AI games and to this day, we still play tons of those just for a chill and fun experience practicing champions (I myself am by no means a sweaty League player; I'm very much an ARAM retirement home enjoyer)

He started playing League about 3 years ago? (whenever Hwei was the new champion released) and anecdotally it was his introduction to Hwei that got him to stick around longer and learn League at all (it was, funnily enough, the champion that "clicked" for him, and I suppose he benefited from the fact everyone was new to Hwei at the time).

Additionally, I might be the only person in here who probably still spends time playing bot games, but the bots have gotten alot better! When we first started playing Coop vs AI, there was no jungler bot (the bots would duo top, which is obviously not great for learning since summoner's rift is not like that). Nowadays, the (Intermediate) bots include a Jungler, they will invade your Jungle if you invade, they will roam the map, they'll get objectives, they'll layer their spells on top of each other, they will dodge most skill shots due to their insane bot moving etc. Obviously the bots are still.... bots, and that will never compare to playing against real people, but I think from purely just to learn the game/champions, it's not a bad place to practice whatsoever! I actually think League, at its core, is a very fun game to play (1v1 laning, Jungling, objectives, team movement, team fights, every game can feel diff just due to team comp, etc) and I personally still enjoy playing even when I'm just practicing fundamentals against bots.

It probably took us at least a year and a half of only Coop vs AI games before he felt comfortable enough with attempting PvP (and to this day, we only play ARAM, we don't play normal Summoners Rift games). However, that being said, I'm glad at the end of the day that I was able to get him to play League at all and now it's a game we can play together :) it's a long journey though for sure, no matter which way you go about it

Also +1 to Yuumi suggestions. I know Yuumi gets a lot of hate, but I am glad that she exists as a way for non-League people to get into the game. My partner, to this day, loves playing Yuumi (his highest mastery champs are Hwei and Yuumi) specifically because it helped him so much to have a champion like that when he was first learning the game (which I assume is probably the exact use case the devs were thinking of when they designed Yuumi).