hello, we still using GXT 4.0.2, and we waited years a fix version because 4.0.3 was a total failure… now we decided to move to “something else”, but we still evaluating different (commercial and not) solutions to replace the client widgets infrastructure.
Also we had a very BAD experience with their support, we paid the fee for years, and in the last times we got a very LIMITED support!
In any case, we are using GXT 4.0.2 and GWT 2.9.0 for a long time without any issue, but we never tested it under Java 11...