With current synchronisation problem between instances, choosing a big instance is a no brainer. I don't want to use small instance and got 404 when searching community on other instance or when not all comments from other instances showed up.

I use Gboard because the prediction is better than the others. As a Japanese speaker, the choice is limited.

Yeah, in the end to move you need your interest (or topic or interesting person you want to follow) to exist in Mastodon. For most people, the topic (or interesting people they want to follow) only exist in Twitter, so there's no incentive for them to move from Twitter.

If their phone stuck in Android 11 in 2023, I doubt there will be any updates from OnePlus.