Seems a few people had the issues too, but didn't figure a solution yet. For example I am having exactly the same this one.
Also according to this a reliable way to test if the universal link set up properly or not is to test the link in the notes app, which works for me. (Also works if I send the message with the link to myself.) However I can't open the app directly in most chat apps (eg. slack, discord) nor safari. On the other hand they works with the preview page on.
Anyone had a fix / workaround? Or that's just how it is (saw this might be issues with app trying to open the link in there build in browser and prevent redirecting somehow ?)
Any help or suggestion will be highly appreciated. Thank you in advance.