Yes, depending on your account.
New sign-ups: If you're invited to Thatch, you can sign up with an email and password. Magic sign-in links and Google sign-in are still the main options, and email and password is the third.
Existing accounts with a password: Look under "or sign in with" on the login page and click Email and password.
Existing passwordless accounts: Passwordless accounts can't add a password themselves yet. To check which kind you have, sign in with a sign-in link and open Profile from the menu under your name. If there's no password field, your account is passwordless. If you want a password, contact support at support@thatch.com.