Sorry, I meant to reply to this last week! If you're using Unity, the Haunted PSX Render Pipeline (HPSXRP) includes the dither filter, along with a number of other PlayStation features. I made this game in UE4 though; the specific post-process material I used is this one: https://blueprintue.com/blueprint/74pz_sk7/. There is also PSXFX for UE4, but that's a bit more expensive.
Thank you very much! And my apologies I didn't respond earlier too haha, I'm not too active on here since I'm quite new on this platform :)
Thank you very much for the response and sources. I'm an Engine Developer so I can't exactly immediately use it, but these sources will definitely help me hopefully create my own one. Again, Apologies and thank you very much!
Ahh, in that case, maybe this will help: https://gist.github.com/ompuco/3209f1b32213cec5b7bccf0e67caf3e9
It's the shader code that's used in the Haunted PSX Render Pipeline; perhaps you can make use of it!