I tracked the CI issues down to linux incompatibility of the vblob polyfill that was being used in the tests. This was causing file system errors during the test runs on linux machines which in turn caused unhandled promise rejections and process termination on Node 15.
Replacing this with blob-polyfill appears to remove the underlying file access errors on Linux and resolve the build failures.
I tracked the CI issues down to linux incompatibility of the vblob polyfill that was being used in the tests. This was causing file system errors during the test runs on linux machines which in turn caused unhandled promise rejections and process termination on Node 15.
Replacing this with blob-polyfill appears to remove the underlying file access errors on Linux and resolve the build failures.