npub1f6a33pfyp67y8llhunlhrf855xm47n3fdqymvxfj7yx78c6vqf4scxpnql (npub1f6a…pnql)
If you search on #FediAdmin there was several posts on actions such as blocking signups from throwaway email address providers and similar options.
Adding a CAPTCHA to sign-up or requiring Mod or Admin approval on new accounts are easier ways to keep the spammers out of your instance 🙂