You can install Sun JDK on Ubuntu. It's not a big deal.
There are still some problems with using OpenJDK, which are being solved now. So, it will be supported someday too.
I've noticed that to the extent JetBrains communicates at all, it has a highly irritating habit of marking issues wontfix and making content-free statements (sometimes passive aggressive at that) until they get publicly called on it, and suddenly it's a completely different attitude.
"Things change quite rapidly" indeed. Is JetBrains not able to keep up?
JetBrains team has its opinions but is also flexible enough to change its mind. And it has been keeping up quite good during the last 10+ years.