This is a gem for serious scholars. They have a searchable digital library of rare Sanskrit manuscripts, including several Puranas that are not easily found elsewhere.
This is a volunteer-driven repository. You will find individual chapters (Kanda) of the major Puranas like the Shiva Purana and Skanda Purana. They are available in Devanagari PDF, IAST, and ITRANS formats. 18 puranas in sanskrit pdf
Shiva, Linga, Skanda , Agni , Matsya , and Kurma Puranas . This is a gem for serious scholars