Thank you very much @Callumfor your post. I was able to install using the command line. I am sure I will find this to be useful information in the future.
My Windows App Installer is version 1.18.2691.0 (Microsoft.DesktopAppInstaller_1.18.2691.0_x64__8wekyb3d8bbwe) and I had not had any issues with it previously. Windows Store Apps troubleshooter reported no problems.
Honestly, I wish Serif would offer alternative installation options. I doubt that Windows upgrade path from version 10 to 11 is a clean process, and troubleshooting Windows Installer issues for even advanced users is difficult. As to the Affinity Apps themselves, well, Awesome! Thanks again.