We don't currently have a speedrun discord server for Cardcaptor Sakura Tetris. There is a general tetris discord - https://discord.gg/0t7Pl8aUFfIHd970 - that may be useful. There are a couple of threads over on Tetris Concept with some information: https://tetrisconcept.net/threads/r-tetris-with-card-captor-sakura.1479/ and https://tetrisconcept.net/threads/tetris-with-cardcaptor-sakura.10/

I also have a personal stream discord server where some tetris talk happens, though it tends to be more centered around TGM than Cardcaptor Sakura, but if you'd like to join, the link is in my twitch profile or you can dm me on twitter or discord.