In Xcode macOS deployment target is 10.15 but on launch, app requires macOS 11.3

Xcode 12.5.1 · macOS 12.0 Beta 6

I have been upgrading a macOS app written by someone else, which has always worked correctly on macOS 10.15 Catalina.

Having finished the upgrades, I find that it no longer launches on Catalina:

However, I have not changed the macOS Deployment Target, which is still 10.15:

I don't know what would cause the requirement for macOS 11.3 — every modification to the program was done using capabilities that were present in the previous version.

I did not modify any build parameters — I only changed the code.

I have updated Xcode since the previous release.

I have done quite a lot of Googling, but I have not been able to find anything. The relevant search terms all turn up results about Xcode versions.

Any pointers in looking for an answer, or even just a direction to investigate, would be very helpful.

Marek H pointed out that I needed to specify a Deployment Target for the target app as well as for the project. Since the field had previously been empty, I didn't notice it:

I entered the correct Deployment Target and the problem was solved: