During the offboarding/separation process, you would want to assign the alumni role (sn_hr_sp.hrsp_alumni) the user. Depending on your company's policies, you may want to update the existing user record and/or create a new local user for their alumni account. I'd suggest working with your identity management and legal teams to confirm what should happen, so you stay in compliance. Then you can determine the best process for getting the alumni registered, but yes, you can allow them to register and have password reset functionality configured on the platform.
