The chronological order of the main series is:
Yakuza 0
Yakuza Kiwami (a remake of the first game)
Yakuza Kiwami 2 (a remake of the second game)
Yakuza 3
Yakuza 4
Yakuza 5
Yakuza 6: The Song of Life
Yakuza: Like a Dragon
Like a Dragon Gaiden: The Man Who Erased His Name
Like a Dragon: Infinite Wealth
How does Like a Dragon fit in it?
"Like a Dragon" is the current series name in the west. It's just replacing the series title. In Japan, the series has always been known as "Like a Dragon".
Are there spinoffs?
Yes. First, there is the Judgment series of two games.
-
Judgment takes place after Yakuza 6 but references very little from that game.
-
Lost Judgment takes place after Yakuza: Like a Dragon and references an unavoidable plot point from that game, but it's not remotely the biggest spoiler of that game.
Honestly the Judgment series can be a good entry point to the series if you want a more modern game to start with.
There's also Yakuza: Dead Souls, a tough-to-get spinoff from the PS3 which is set between Yakuza 4 and Yakuza 5 but is non-canon and is about zombies. Don't worry about that one until you're WAY deep into the series.
There are also some entirely unrelated spinoffs:
Like a Dragon Ishin! is a spinoff set in the 1800's where you play as historical characters that have faces from the main series.
Fist of the North Star: Lost Paradise is another spinoff only available on the PS4 which is ostensibly just a Fist of the North Star game in the Yakuza style, only many of the characters in the game use Yakuza series voice actors.
Do I really need to learn that tiles game whateveritisnamed that had a manga with SSJ Hitler?
Mahjong is a fun game and if you want to learn how to play I can teach you. If you want to teach yourself, check out Mahjong Soul as it has a decent tutorial.
Is GamePass missing any game?
I don't think so, but granted I'm not on GamePass so I can't confirm. There was a time where some of the games dropped off GamePass but they might be back on?