Of a well-known manufacturers, I noticed Xiaomi to do some real shit: it had an app preinstalled that displayed ads above other apps. But at least when I identified the culprit, it was possible to remove it completely and the problem went away.
Got a new phone at some point and tried it again, and they were on some real shit by then. All the default built-in programs for like, /music playing/ would force you through a Xiaomi Cloud sign up process just to play music /already on your phone/.
Granted, Google is now on the same shit; I found with my latest android they've removed all the basic apps for file browsing, music playing, and the like. Now only "Google Play" versions remain, that of course require a Google account.
I feel like the camera and calculator are the only non-play-required default apps left, but I won't be surprised if I find one day that the camera is somehow integrated into Google Photos, which will of course not open until you sign in.