If you want to screen who follows your account on Mastodon:
1. Log in through your server’s website or Mastodon web app
2. Click on your profile image to go to your profile page
3. Click on "Edit profile"
4. Click on "Privacy and Reach" tab
5. UN-tick box marked "Automatically accept new followers"
6. Click "Save changes" at bottom of page
Any new follows will need your approval, and a padlock 🔒 will appear on your profile.
More info about this on fedi.tips website: https://fedi.tips/restricting-who-can-follow-you-in-mastodon/