[giskou]

I have been receiving notifications that a person in my contact list is now using Signal for years.

Apart from that, your use case has another possible issue. If a person stops using Signal, your messages will go to the void until Signal actually removes the user and your client switches back to SMS. This has caused a lot of confusion for some of my friends when I switched my signal account to a different phone number.

I think it's more reliable to use Signal for Signal.