The question about monetization is incredibly important when funding a Mastodon instance.
Therefore, it's important to consider how they get their funding. For example:
* mastodon.social is run by a non-profit
* social.coop is run by a cooperative
* vancity.social is run by a hobbyist (me!)
Ask the instance admins about how they acquire their funding.
One more note: if a person saying "Don't donate to a non-profit" is running a for-profit instance, take their advice with a heaping tablespoon of salt.