It appears to be a pretty fantastic time for full-stack development and solo founders. For me, the context switch between client and server was always difficul

It appears to be a pretty fantastic time for full-stack development and solo founders. For me, the context switch between client and server was always difficult using a Scala/TypeScript setup (startup). As you said, unless you rely on some niche technology only available on the JVM, it‘s probably more productive to go full stack TypeScript. For perf-heavy workloads I would probably pick Rust instead of Scala.