Please stop suggestion there's some sort of "quiz" when signing up to Mastodon to pick a server, that's ridiculous:
1. Adds friction to signup
2. Can be seen as invasion of privacy
3. Will just create a “who gets on the curated server list" debate
Instead, default people to a large generic instance (e.g. mastodon.social).
Optionally, after a while, look at people and hashtags they follow/post/interact with and _then_ make suggestions; use directory data from joinmastodon.org to match.