[thwaller]

Tmm is compatible to Java 11, but unfortunately there is more than just to be compatible...
we have 3 different OS with at least 2 different Java versions of 2 different vendors (and since almost every Linux distribution packages its own openjdk built there is much more variety..)

I can say that tmm works on all 3 OS with Java 8 and Java 11 (at least I am not aware of any bug at the moment..) we're also running many unit tests on java 8, 9 and 11 and no one is failing..
Myron runs windows (iirc oracle Java) without any issues and I run tmm myself on manjaro with Java 8 and 11 (openjdk) without any issues.
keeping this in mind your problems must have something to do with your setup

I've chosen Java 8 years ago because it can run on every OS, but lately I need to find/fix issues (which are caused by specific OS/Java combinations) more than developing tmm itself and this is very frustrating..

We try to make tmm as generic as possible to be run everywhere but there are limitations... And I am aware that we can't help everyone (there is just not enough spare time to help everyone and keeping tmm developed), but we try to do as much as possible

I have considered my setup, but I struggle to find it. I do not use Java for much of anything. So once I had this issue, I simply removed all of Java and reinstalled fresh for each test. So each Java install was to all defaults as set by the maintainer. I completely understand the frustration of spending time on compatibility issues vs improvements, which is why I asked on the direction you take. The best I can do to be compatible is to use default installs and change nothing, or as little as possible.

Where I am getting confused on this ... OpenJDK 8 works just fine. If I uninstall it and install OpenJDK 11, it is broken. If I uninstall that and install Oracle Java 11, it remains broken. Uninstall again and install OpenJDK 8 again and we are all good. During the above, I also tested my Java app MP4Box GUI, which runs on Java. That app ran on all three environments of Java. Although the above cannot rule out something on my system, it does show that it is related to Java 8 vs Java 11 and the working of tMM with it.

Since I can work just fine on Java 8, this is not really critical, but it does throw a few caution flags.