Thanks, @javahippie , your thoughts and references are very valuable. Sounds to me as if there is still now hurry to rush. My main concern was about our own dependency stack. From implementation side, there is no reason why we would need Java 21 as minimum. There is this or that in the API that would make things smarter (e.g. List#getFirst(), switch pattern matching), nothing urgent.
What is for sure is if we would decide for a Java 21 baseline, that this requires a major release. We should not fear increment major versions if required. Breaking is breaking, even if it just means to change the JVM. So if we decide to raise the baseline, it must be with 2.0 or 3.0+, not in 2.x.
We are already close to 2.0, so we have to decide soon in favor of it, or wait at least 1 year.