Work on a template locally and see exactly what recipients will get, before you publish.
samva templates dev --open
samva templates render order-shipped --fixture default
samva templates snapshot order-shipped --fixture default
dev opens the visual editor with no setup. render prints a fixture's subject and text, or its HTML. snapshot saves desktop and mobile screenshots, light and dark, to .samva/snapshots.
What you need to do. Local commands now use the compiler your project installs, and a defineEmail entry is reported as an error. Move those entries to defineTemplate before you upgrade. The package changelog has the rest.