Force user password reset

I’ve imported users from an opencart site to Magento 2. Logging in obviously doesn’t work, but when I try to use “forgot my password”, it doesn’t work either.

The only way that I can get the accounts to work is by clicking “reset password” on the admin side.

Doing this one by on ins’t an option (over 10000 accounts), so is there a way to bulk reset everyone’s password so that they’re prompted to create a new one the next time that they attempt to log in?

Alternatively, is there a way to get “forgot password” to work for imported accounts? If there is, I can just add some text to the login page telling them that if this is their first visit to the site, they have to reset their passwords.