let’s start with - Do you remember if you migrated your SmartThings account to a Samsung account? if yes, that may make things easy and I would suggest installing the ST app and logging in with your Samsung account. Check if your hub shows in the app.
If you didn’t migrate to a Samsung account… reply back.
I am/was in the United States and signed into my Samsung account and it shows SmartThings under apps and services. Used same account to sign into the SmartThings app and there is no devices listed. Tried to add hub but it’s asking me for a welcome code I don’t have.
Other than that I don’t see where where I migrated.
Last SmartThings email was October 15th 2020
Subject: Thank You! Partially reading “See you soon in the new app!”
The day before email
Subject: Hurry! SmartThings Classic will be discontinued tonight!
The welcome code is easy to get. Post in the following thread and list the serial number of your hub. ST staff generally reply to you with the code when they are available. also check the inside of the battery compartment cover