Same issue here. Not only is the image on iOS always black when on macOS it displays as expected, but on iOS some images are also displayed with a slightly wrong aspect ratio, as demonstrated by this code:
import SpriteKit
#if os(macOS)
import AppKit
#else
import UIKit
#endif
class GameScene: SKScene {
override func didMove(to view: SKView) {
let systemImage = "square.and.arrow.up"
let width = 400.0
#if os(macOS)
let image = NSImage(systemSymbolName: systemImage, accessibilityDescription: nil)!.withSymbolConfiguration(.init(hierarchicalColor: .white))!
let scale = NSScreen.main!.backingScaleFactor
image.size = CGSize(width: width * scale, height: width / image.size.width * image.size.height * scale)
#else
let image = UIImage(systemName: systemImage)!.applyingSymbolConfiguration(.init(pointSize: width))!.applyingSymbolConfiguration(.init(hierarchicalColor: .white))!
#endif
let texture = SKTexture(image: image)
print(image.size, texture.size(), image.size.width / image.size.height)
let size = CGSize(width: width, height: width / image.size.width * image.size.height)
addChild(SKSpriteNode(texture: texture, size: size))
}
}