Please try to install RGT Screen via direct download from RGT (the install .msix requires Windows10 with Microsoft Store installed, however you do not need to be signed in to the Microsoft Store for the installation to work): https://www.rgtcycling.com/downloads/RGT_Screen_installer.msix
If you are unable to install the package on Windows10, it is possible that you need to install the Microsoft App Installer for Windows 10:
https://www.microsoft.com/en-us/p/app-installer/9nblggh4nns1?activetab=pivot:overviewtab
Please download that first, then try installing the RGT App again.