TLDR: Has there ever been any canon speaking lines for Slytherin or Gryffindor's portraits?
A bit of context:
According to wikia, the canonicity of Harry Potter works is broken out into 3 tiers. The Wizarding World of Harry Potter, at Universal Studios, is listed under Tier 2 Canonicity. Which means everything there falls under this description:
These sources do not contain information directly from the "mouth" of J. K. Rowling, but they are projects based on works by her, and in which she was involved in some capacity at some point.
While in line for Harry Potter and the Forbidden Journey, there are lots of cool things to look at, as well as speaking portraits who talk to each other. In one section of the line, the portraits of Salazar Slytherin, Helga Hufflepuff, Godric Gryfindor, and Rowena Ravenclaw speak to each other. The main conversation is about Harry Potter, and how all the founders say things like "Godric, you must be so proud to have Harry Potter in your house... etc etc." while Slytherin says things like "HAH, the boy who lived!? bla bla bla" (obviously not direct quotes).
This got me wondering: firstly, are there actual speaking portraits of the 4 founders at Hogwarts? Doing a little research, I found that both Gryfindor and Slytherin have portraits in the Entrance Hall, and a portrait at the Grand Staircase and the dungeons antichamber respectively. It's probably safe to assume the other 2 founders have portraits as well, but they've never been mentioned.
Given that these portraits do exist, are there any canon speaking lines for Slytherin or Gryffindor’s portraits? Gryffindor speaks proudly that Harry Potter is in his house at the Universal Studios ride. Has Slytherin ever mentioned how proud he is of Voldemort or have they ever spoken on the events happening at Hogwarts, for example? Or really, have either of them ever spoken at all, in any capacity (in tier 1 canonicity)?