I've tried finding a single Slime (the mob) for days on the new release of Minecraft for the Switch and I haven't been able to find anyone.
I've tried looking in swamps waiting for full moon nights and even removing the water to the bottom, under layer 39 in different adjacent slime chunks while removing any other mob (mainly Drowned) around the place and not even after several days waiting from the distance a slime has appeared.
Also, to check if this was due to other factors (such as underground caves filled with mobs), i have converted an old world I had in Survival mode to a new one, and changed the mode to Creative. After that I went to a swamp I previously explored in the old version for Nintendo Switch and I used to farm Slimes during the night, and after setting the time to midnight with full moon and killing any mob in the world which was not a Slime, all through commands, I waited to see if any Slime spawned in the area, but only Drowned and one Spider appeared.in the whole night.
That's why I'm assuming this has to be a bug, because in the older version I had no problem at all with Slimes. It's kind of frustrating, since I've tried a new Survival game with the new Aquatic Update, but without Slimes I can't do many redstone stuff, guiding animals, nor prepare fire-resistance potions for the Nether (btw, Magma cubes don't spawn either, I've tried too), so I hope it can get fixed somehow.
I don't know if there's rather something I'm doing wrong, but I haven't seen a single Slime in all the game and it's really rare.
I've thought it might be due to the high rate of Drowned spawning introduced in this update, which in addition to the low chances of Slimes to spawn might have reduced significantly the real chance of a Slime to appear (however, I don't understand the Magma cubes issue).
Related issues
Comments


You might want to add your vote to MCPE-21856 (general mob spawn issues). On Xbox One I seem to get a few nighttime hostiles on the surface (nothing in caves), but like you I have never seen a slime. There is a huge swamp near my spawn point and no slimes have ever spawned there. I have also explored caves and ravines for hours and never found a slime. Makes getting a horse lead difficult.

Done.
Thanks for the advise! Hope it gets fixed soon...
Thank you for your report!
However, this issue has been closed as a Duplicate of MCPE-21856.
Please add a vote and any new information to the main ticket, which will be updated accordingly.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Feedback – 📖 Game Wiki
Also, I've noticed that the darkness spawn rate of any other monster is extremely low compared to what I was used to.
In all the game, after exploring a really large cave I've only found two skeletons and a few zombies coming from a monster generator.
It's causing the game to be quite boring without any chance to be surprised nor get rare materials such as string from spiders.
The only place where monsters spawn in decent rates is in the Nether (Not visited the End yet)