Cydia Impactor was not been updated for iOS 13 so the best alternative we have now is nullxImpactor [DOWNLOAD]. This software will let you install apps without a developer account into your device.
nullxImpactor New alternative cydia impactor for iOS13
This tool has been made by @nullx but most of the work has been taken from @rileytestut. this tool is Similar to the AltServer for Windows patch by @InvoxiPlayGames, @nullxme built a Mac app based on AltStore that also lets you sideload any app (.ipa).
You can also check this new tool to install apps and jailbreak tool. Alternative to Cydia impactor windows and Mac.