There was the alternate ending of the S1 finale where Leland was originally introduced and he recruited Georgiou, which was posted online in March 2018, but, yeah, that's the only real pre-season 2 material involving Section 31.Because I don’t recall Section 31 even being a thing until season 2.
I guess, there were the guards with the black badges seen early in S1, but we didn't know they were Section 31 until it was later retconned that black badges meant Section 31. Indeed, they seemed to have been forgotten when Section 31 was introduced on the show, given in S2 Tyler mentions having been aware of Section 31 but never having met anyone from the organization. An odd statement from a guy who served on a ship which had a couple of Section 31 agents assigned to it. And even odder statement if said ship was supposed to have been commissioned by them.