Undub patches can be so easy in the PS2 scene people may undub patch games for themselves but they don't share it and use it only for their private fun, some of these people may think "dude it's so easy people would do it on their own anyway" lol, not to mention there is no dedicated website to share such games anyway (there is only for sharing these patches instead). For example I sometimes change soundtrack of PS2 games and these modded PS2 games may be uploaded on this website which this website is the only website I know for a way to share changed games but honestly it seems so much bother to share this on this website so I don't lol. Instead I give people tools to mod their own game + the modded file lol.
How to undub games?
1 - USBUtil v2.00
This program does lots of stuff so it also let you see files in a PS2 game, extract and replace the files. This is simply how you can take videos from a game and replace the target game's videos (this is how I rip PS2 games to reduce their size). People embed subtitles and thus replace these videos for example. But this program always fails to extract files when it's fine to replace files. To extract files use USBUtil v2.2 rev1.0 (Beta) but it's not English.
However if the target game's file you wanna replace has bigger size than the file you wanna replace you gotta rebuild the whole ISO via CDGenPS2 v3.0.
2 - CDGenPS2 v3.0
Just put the content of the game into this program and "save image" as ISO and you are done.
But the actual bother of undub patches is finding sound files in AFS files (simply put package of sound files in one). For it you can find many programs that we gotta thank PES community for that lol.
3 - AFSExplorer 3.7
This is the main program I use a lot to change sounds. It allows you to export and import files. If you gotta convert sound files to what a PS2 game can play then gotta use ADX_Sound_File_Converter_1.4. ADX files are sound files inside AFS files.
X - Sometimes it's not that easy.
For various reasons the game files may be compressed and it cannot be extracted via generic programs like Winrar. Then gotta figure out how they are compressed and find your way to extract them and then find a way to compress them back. However I don't remember seeing a PS2 game having compressed sound files which would make sense for technical aspect but IDK it is not impossible to find I guess.