A version of powershell7 for Debian 10 (buster) is available here. However, it depends on the Debian 9 (Stretch) versions of libicu and libssl (57 vs 63, and 1.0.2 vs 1.1 respectively). In its current state, this is not installable without pulling in old versions of the packages from Stretch, which is not recommended. Will you be building a version that depends on the newer versions of these packages?