I started this experiment with one question in mind: could you realistically use an Android phone in 2018 with only open-source software? I think for most people, the answer is no. Just about every service or app used by the general public is closed-source, and unless you're willing to switch away from Google's ecosystem and go without most apps, it's just not practical.
I totally respect people who use open source things when possible, but it’s nice for small things here and there, not a way of life for most people. This experience seems miserable to me.
It also speaks to how “Android is open source” is basically just a talking point that is technically true but is not effectively true for anyone. Even if you install an open source ROM on your phone (already putting you in the top 1% of users) then you can’t use a single Google app or service, or Slack, or Discord, or Twitch, or basically anything you’ve ever heard of. There are a few apps that do kay, but the experience with most of these alternatives sound like a pretty terrible experience.
Open source is great for small tools that developers can use to create cool software, but the open source app options for actual user-facing software is, as it has long been on Linux desktops, pretty terrible.