This one does not require a Developer Account, but you will need to sign in to your Microsoft account.
If you own a Windows 10 Mobile smartphone, you can also install apps to it using a Web browser. How to download apps on a Windows 10 Mobile device using a Web browser The limitation with this method is that you need a Developer Account for it to work. This method is important because the Windows Phone 8.1 app store was shut down in December 2019, so this is perhaps the only way to get apps on them now. Select the applications that you want to install.Open the store app on your phone and then tap SD card.Reboot your phone and wait for 1-2 minutes.Click the Download and install manually link down the bottom-left of the page.Select the app to open its details page.
XAP files are native Windows Phone app format. If you need to download apps to a smartphone running Windows Phone 8, or higher, and it has an SD card slot, you will be able to. How to download apps on a Windows Phone 8 device without using the app store