Hello @DSEyers!
What you are trying to do seems reasonable… before SQ 8.1! Ann detailed on this thread the 8.1 changes, an important one is that we merged Short Lived Branch and Long Lived Branch into… just Branch! Read the MMF-1786 if you want to know more.
Therefore, sonar.branch.name is now only used to analyze a branch. sonar.target.name is no longer supported because it was for Short Lived Branch.
What you have now (since some time actually) is Pull Request. Pull-Request analysis allows you to “compare” the Pull-Request code with its targeted branch, now set with sonar.pullrequest.base.
The whole feature extends to also decorate Pull-Request in the ALM, but if your tool chain does not allow that, you can simply analyze your code as such.
Does it make sense to you?