Same situation here, got around the problem by adding library A as a new product of the package. e.g.
let package = Package(
name: "PackageB",
products: [
.library(
name: "PackageB",
targets: ["PackageB"]),
.library(
name: "LibraryA",
targets: ["LibraryA"])
],
targets: [
.binaryTarget(
name: "LibraryA",
url: "https://url.to/LibraryA.xcframework.zip",
checksum: "checksum"),
.target(
name: "PackageB",
dependencies: [
"LibraryA"
])
])
Then add both libraries to App's Frameworks, Libraries, and Embedded Content.
Still would like a better solution.