Deprecated means that people should not start making new apps using an interface. It doesn’t mean that existing applications are about to die.
Apple has a huge number of APIs that were deprecated 5-10+ years ago, but which are still working. It would be self-destructive for them to break OpenGL quickly or without a huge period of warning. Think about all of that revenue that they earn from micro-transactions in OpenGL-based iPhone games.
We have had plans for a while to move Roon’s rendering engine over to something from a 3rd party that can sit on top of to multiple hardware rendering interfaces (DirectX, OpenGL, Vulcan, Metal, OpenGL(ES), etc). This will improve performance, make the app smoother, increase our capabilities with regard to animations/transitions, and as a side benefit, it will help us get past this kind of stuff.
If for some reason Apple decides to move much faster than usual on this, we’ll just speed up that project. No big deal. Keep calm and carry on…