Sideloadly will ask for your Apple ID credentials to sign the app. This is a standard and safe process. If you're concerned, you can create a brand new, secondary Apple ID specifically for this purpose.
Trick the App Store into letting you download older, compatible versions of apps.
Enter your Apple ID and password (this is required by Apple to sign the app for personal use; using a burner Apple ID is recommended for privacy). Click to install the app on your iPad. Step 3: Trust the Developer Profile