Single argument to --targets is still fine, but multiple targets are not. Now when you say deploy --targets .#{host-a,host-b}.system you get:

error: the argument '--targets <TARGETS>' cannot be used with '[TARGET]'

Usage: deploy --targets <TARGETS> [TARGET] <EXTRA_BUILD_ARGS>...

The commit in question "just" updates deps, perhaps the Clap major-version bump is the problem?