where led me to a big hill that didn't look like a Swamp at all but still dug down where there was a slime chunk next to the swamp biome to about level 60. So there must be some compatibility issues with the Nintendo switch? I don't know...
*I've kept the area well lit so no other mobs spawn.
* I've gone hunting for other mob nearby that are causes the Slimes to not spawn
* The Ravine wont effect the Slimes spawning because the ravine is like +100 block away
Previously I had my best luck in a surface ravine - low Y value for floor, and sky access. Slimes spawned consistently on the bottom and I got my main starting supply from hanging around there a few days. Until last night I had never actually seen a slime underground, but I did finally find one tiny one wedged in a 1x1x1 opening at the edge of a pond at Y=11 (completely underground in a cave system).
I also spent waxing 3/4, full, and waning 3/4 moon in a swamp (3 in-game nights) and did manage to get 1 large slime, 2 mediums, and a small, for a total of 27 slimeballs. Fine for single-player, but much worse than it used to be.
Slime chunks are everywhere and any cave system of moderate size ought to cross a few, but the critters are more rare than emeralds it seems. Open a flat world in Creative and approximately 2.73 billion slimes will spawn around you (at Y=4 and full sky access). I personally think the game has a bug regarding sky access for slime spawning, tho that one tiny guy I found last night in the underground pond throws a wrench into that idea.
It's not a bug as much as it is flawed design. You see sky access spawns because the surface mob cap pretty much gets reset every day/night cycle. For cave spawns, once you've loaded the chunks and they spawn there, they stay there seemingly forever, trapped in a small air gap never to be seen.
They could fix it by changing how the game despawns cave spawn mobs, making it despawn at a much shorter distance and at a much higher frequency.
In one of my current world's, all mobs had disappeared around my main base area and were gone for days, finally noticed when walking around 6 drowned in a little pit of water not far outside the base, taking up the mob cap and keeping everything from spawning. They have a long way to go with these mechanics.