The 8.x LTS is still a long ways off, the expectation (nothing is settled until it is actually done) is that SonarQube will begin requiring Java 11 on the scanner side sometime in the v8.x release cycle.
While there may be support for Java 8 from certain vendors until 2023… to use Java 11 features on the language analyzer side (and to prepare for the future!), that transition period starts earlier!
Well, I manage an (Enterprise) instance for >400 developers and not all projects are on their way to use a recent JDK. Anything helps to nudge projects a bit