is it possible to backport the mesence changes into current libretro core?
Yeah, probably the best move is going to be to finish cleaning up my libretro-ization and then just apply that to the CE version.
Can’t you do this using one of the good NTSC filters that already exists, for example CRT-Consumer-XL, DariusG’s port of Blargg NTSC, CRT-Guest-Advanced-NTSC and CRT-Guest-Advanced-NTSC Decoupled, Classic Scanlines Shader?
Besides that, you can disable the internal Core Blargg NTSC Video Filter and utilize some video filter presets in the Settings–>Video–>Filters Menu.
You can also get extra custom Blargg NTSC Filters in my CyberLab Custom Blargg NTSC Video Filters Preset Paclk but they as well as the ones I mentioned above are based on the Blargg SNES NTSC Video Filter.
I am a bit confused because I thought MesenCE was a fork because Mesen has not been updated in a while. But it seems SourMesen is active and doing Pull Requests and updates for MesenCE. I find it strange that a fork gets updates from SourMesen, but not the official version?
I think it had something to do with the license of Mesen2