and VLC just plays the main movie from the disc.Java required: This Blu-ray disc requires Java for menus support. The disc will be played without menus.
I have openjdk-8-jre installed. Both VLC and openjdk are installed via apt and not via snap or something. I had this problem before until is was fixed in, i believe, 3.0.2. From that on it worked perfectly in Ubuntu and Manjaro. Then, after upgrading Ubuntu to 20.04, the error returned.