for android apps, the mobilism forum is great, thoughb only questionably safe, I guess. it’s all one click hosters, which sucks, but the apks are usually small enough in filesize to not make it a big deal. Just come armed with a good ad blocker, I guess. You can also try your hand at cracking/patching apps yourself, right on your phone with stuff like lucky patcher

for switch, I’m not sure, they’ll usually be among other gaming torrents on all sorts of trackers in my experience