www.makemkv.com

Maybe it was just a bad disc. I tried another with "Custom Java executable location" =/usr/bin and got:

Processing BD+ code, please be patient - this may take up to few minutes
Processing BD+ code using generic SVQ from builtin/generic.svq
BD+ code processed, got 1 FUT(s) for 1 clip(s)

I tried ...

It is also size 0. I only listed that because makeMKV kept using that if I used the Java selection instead of typing in a path.

FYI, the disc failed to play last night in my PS4 and only played about half in my PS5. I wouldn't think that caused the problem because I think it looks for Java before ...

Java 1.8 is in /usr/java/jre/bin.

Using Java runtime from /usr/java/jre/bin/java
Failed to execute external program 'java' from location '/usr/java/jre/bin/java'

/usr/java/jre/bin/java -version
java version "1.8.0_301"

I also tried the directory without "java".
Using Java runtime from /usr ...

This disc requires Java runtime (JRE), but none was found. Certain functions will fail, please install Java.

Using Java runtime from /run/user/1000/doc/1dee089c/java
-rw-r--r-- 0 USER GROUP 8.8k Jun 9 2021 /run/user/1000/doc/1dee089c/java
Failed to execute external program 'java' from location ...