It's still in theatres in Japan. It had a limited run in Korea a couple of weeks back but that might be over now. Otherwise, we just have to wait for it to be released digitally and physically, which can take a few months.
How to watch with subs though? I did try joining the discord but still no updates
The soft subs are on the website itself. However, I did read that due to a bot problem, the site is not open for registration at the moment. You may want to check out the comment below that may have it in a different discord.
The screenwriter Ueda Makoto really likes playing with time. The more I think of this movie, the more I feel like I need to map it out more. It really is an interesting take, though!
https://x.com/kaede_movie1219/status/2042409588549697874
https://www.vap.co.jp/stmoon-movie/