not using visual studio or mac, but by the looks of it there are at least 3 paths you can try.
1. Assuming you can configure the C# version used in the project, did you verify using the correct version?
2. I would expect “CS8025 fix” to be searchable at the Internet with explanations how to fix. This holds pretty much for any standard problem, you’re not the first one encountering it, and people write about everything at the Internet.
3. While “interpolated strings” may not be supported, I am sure you can make strings in C# versions 1-5. Find out how, and change the code so you don’t use interpolated strings.