so congratulations.

Yeah that one was on me being stupid. And it didn't prevent me from buying an LG 4 afterwards.

you can find the app package name quite easily by long-pressing the icon of the desired app on your phone,

Yes, but it doesn't say the file name, which is what the ADB uninstall tools use.

I ended up returning it, it showed one advertisement too many (premium wallpapers!), and security center can't be uninstalled. I don't want to use custom ROM anymore, If I plan to have a phone for 3-4 years, I'll have to go through the hassle again to upgrade.

Too bad really, because the hardware was amazing, and it worked well apart from the bad MEUI decisions and shenanigans.