Solution found. My 'Other Linker Flags’ build setting was set to -Wl -exported_symbols_list /dev/null since earlier in the year, when I was testing app size reductions. This worked fine with local builds with Xcode 15, but just started causing an issue with local builds using Xcode 16. Removing this custom build setting value fixes my issue entirely.

Same issue with Xcode 16.0 (16A242d, final release) and macOS Sequoia 15.0 (24A335, final release).

Update: I'm wondering whether I either have some local project or tooling corruption, or should have been running macOS Sequoia this whole time. Building and distributing a TestFlight build from Xcode Cloud (macOS Sequoia RC + Xcode 16 RC) is successful, and the resulting app runs with no issue.