I know what you are saying. There isn’t a lot of guidance on regular controllers either. I pester my 20 something and 30 something-year-old sons on what buttons do what.
What I’ve found is there isn’t a lot of consistency even with normal game controllers. Somethings like the up/down/left/right buttons can be obvious, but even things like “Fire/Attack” can vary between the right trigger and the A/X button. I’ve been playing Fortnite a lot so I’m getting really biased by their use of keys.
The point is that you probably should figure out how your players are going to hold the controller to play the game (vertical one-handed or horizontal two-handed fashion. Find out what buttons feel natural to use for your actions.
Also consider having multiple buttons per function. For instance, in the game I’m working on, the primary weapon is on the right trigger, the A (Xbox), X (Playstation) buttons, the space bar, right shift and mouse click/screen touch. For Up/Down (the only two ways the player can move in this game), W/S (from the WASD keyboard standard), Up/Down arrows, on the controllers both the Up/Down D-Pad controls and the left stick axis and touch controls. This lets the player use what’s comfortable to them.
Rob