@leonard84 is right, the ensuing juggling of runtime class file versioning becomes burdensome. @dmeneses, supporting Maven Toolchains should be “rather simple.” It’s possible there is some underlying Sonarqube complication, but the reference is there for consideration. Additionally, no forked process is required. The instruction runs in the current Maven session as I understand the implementation, or forked automatically.
Maven Toolchain support would be a huge win and is the way to go IMHO. Additionally, “down compiling,” i.e., building 1.8 with an 11 JDK (the current requirement), is risky, albeit an unknown risk, especially if your legacy code is lacking a full test suite for confidence.