The downside is that you lose DRM-enabled content. For example, it's a hassle to use Netflix at 720p/1080p, and what's more important to my use case for example, is Spotify. It's _possible_ in theory, but it's extremely hacky.
I personally went the Google route w/ a Pixel 4a, so I get a simple, zero non-sense UI, with no forced ads or anything, just a smooth experience, at a slight premium (not that much to be completely fair ...)