I’m assuming when you “reinstalled the OS” you just repartitioned the drive and installed normally without encryption for the person? If that’s the case then all your old data is encrypted and will be unrecoverable without your password and the LUKS header.

If however you reinstalled the OS within the already made LUKS partition and are giving them the password (for some reason) then yeah, you wanna secure erase it.

If you were selling on eBay or something I would still recommend a secure erase (they’re really quick on SSDs)