what version of the JVM are being using as the target for their plugins these days? I currently target 11 for most of my plugins, but per the compatibility matrix, it looks like I could bump that to 17, unless I'm misunderstanding?

If you only target Gradle 9+, then yes you can use 17 without concern as the Gradle daemon will always be 17 or higher.

that's what I thought. I wish the compat matrix were a bit more clear on the "9+" part. I shouldn't have to find the version of the compat matrix from Gradle 8.x to see old requirements. The compat matrix "feels" like it's meant to be true for all extent releases

If you build For plugin consumption then it needs to be as wide as possible. We still build a lot of them against JDK8 because we target 7.3+. But as @Octavia Togami said, it depends what you target. If you build in-house only you can do what you want.

it might depend on the ecosystem as well - Android Gradle Plugin 8.0 and later requires JDK17+

for the plugin I'm thinking of, I advertise support for Gradle 8.11 (works with both JVM and Android), so I'll stick with JDK11 for now. But thanks everyone for the feedback!