Hey,
I had the same problem when I updated my iOS version, however There’s a solution. (Well, sort of / it will open the app on the subscriptions page and not the home page)
- open your YouTube app
- press the top right corner to go to your profile
- press settings
- On settings search for ‘siri shortcuts’
- Now there’s a menu with several options.
- press on ‘open subscriptions page’
- Now you have an option to type a phrase (‘when I say’) - type ‘Open YouTube’.
- save to shortcuts
- close YouTube
- say ‘hey siri open YouTube’ - the app will open. Only different it’ll open on your subscriptions page and not the home screen.
you can type any phrase you want and also there’s more options on that menu as you can see.