How to change PHPBB password encryption method?

Question

PHP

There is a Minecraft server. There is already a ready database of login\passwords. All passwords are encrypted in sha256. You need to somehow connect phpbb to this database for authorization using these logins / passwords on the forum. There is no registration on the forum. I found a way to connect authme (plugin for authorization on the server) to the phpbb database, but then the players will have to re-register. Therefore, you need to somehow, perhaps, change the type of encryption on the forum, disable the salt ..
Maybe there are ready-made plugins to solve this issue? Or can you tell me where to dig?