I imagine it would be on Paramount+ as that is where Showtime merged and Dexter was an original Showtime production, but I could be wrong.
I just finished watching the original Dexter on Netflix...again. I like to watch the series about once a year. I have also watched New Blood twice. I just love Dexter...wonder what that says about me...LOL!
I have also been watching Six Feet Under, with Michael C Hall, also available on Netflix. I had not seen this one in year and it is such a great show.