I am also following Nick Brazzi's video and doing fine up until the 11 minute mark when I switch to Anaglyph view.
I have attached two screenshots. One shows after applying the STMap that there appears to be an error with the equirectangular calculation. The 2nd shows the that when I switch to Anaglyph view it stretches the image across the frame rather than showing the two squares overlaid.
I can change the view to square if I change my image scaling settings in project settings but this does not match what Nick was doing in his video and means I would have to switch back and forth for each shot to set my convergence.
I also included a screenshot of all the Kartaverse packages I currently have installed as this was also different for me than what Nick showed in the video, in case that is relevant.
I am using the generic ST map but I could work on a custom one if that is causing any issues.
Any help would be appreciated and thank you Andrew and Nick for providing this amazing resource!