My iPhone is iOS 13.5. The Software Update is apparently updating to iOS 14.4. Is this normal?

Yes. iOS devices can only be updated directly to the latest compatible release, or to a beta for people enrolled in the program.

(192037)

Yes, since the current iOS version is 14.4.

Settings / General / Software Update

You must use a W-I-Fi connection, have 50% battery, no VPN or hotspot.