I Believe you will still be able to use it without a region lock, but you now have to do two things:
One) enable developer mode and
See the following FAQ:
FAQ: Did we lose the ability to add custom smartapps after the app update of June 2021?
All of that said, smartthings is intending to discontinue the Samsung hosted Groovy cloud soon, so all custom smartapps will have to be rewritten or moved to a customer hosted server.
Changes to the Legacy SmartThings Platform
The explosive growth of our community and platform over the past few years has been an amazing experience for all of us at SmartThings. We have you to thank for building, innovating and growing with us as we push the envelope to what is possible in the connected home. Today, we wanted to let you know about the next evolution in our journey.
We are making some important shifts in our strategy to best position our platform for the future and investing more deeply in improving the stability and security of our platform. With these changes, we will empower a broad ecosystem of developers to integrate and innovate with SmartThings using technologies of their choice.
Over the course of the next several months, we plan to focus on the development of a …
and all custom DTHs Will have to be rewritten.