Gradle 7.6 Toolchains support Java 21?

According to the Gradle Compatibility Matrix, Toolchains of Gradle 7.6 support java up to Java 19. (Java 21 support was only introduced in Gradle 8.4). As far as I understand these versions are not actual limitations, but rather versions that were available at that time and Gradle has been initially tested with. So this doesn’t mean that Gradle Toolchains will not work properly with never versions of Java.

A quick experiment shows that there is no compilation issues as well as no issues with running unit tests when Gradle 7.6 Toolchains configured to use Java 21 (./gradlew is on Java 11). e.g.

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(21)

So I have few questions to experts:

  1. Is there any official or non-official information related to compatibility of Gradle 7.6 Toolchain and Java 21 (besides Gradle Compatibility Matrix)?

  2. Is it possible and how to test toolchain compatibility using tests of Gradle Project (I tried to use -DtestJavaVersion=21 flag, but faced with build issues)

  3. Are there any well known or potential problems with given configuration?