[deleted] Tbqh, as I said I had to struggle with IBus, especially since I can't read Japanese, so maybe it's beginner's luck but at least it shows there is an easy way to get it working.
Do you know if you have to same issue on other linux MATE edition (other than Solus) ?
With Solus Budgie & Gnome it works fine, you don't have to switch to English to get IBus working fine, do you?