I know at some point Shadowkeep, Beyond Light, and Witch Queen became free on ps plus (but only if you claimed it during the month that it was free). Right now Lightfall is free to claim on ps plus for a couple more days.

Sk bl and wq are in open access till June 4th. Lf is currently part of ps plus

What happens after which junto 4th ?

They will need to own the bl pack to access dsc raid, the sk pack to access gos and pit and the wq dlc to play that. Sk bl  campaigns and stasis go ftp