If you have any other issues getting WHMCS running, hit me up here. I just spent a few days getting a very specific WHMCS install working on Enhance. One thing is that the modules that dial home (if you use 3rd party paid extensions) will choose the local container IP.
This may cause an issue with some vendors, but, after I contacted them, all of my vendors made adjustements.
I also have some very specific plugins that do not like php 8.1/8.2 so I have had to revert back to 7.4 temporarily.