I’m still trying to figure out if I can use transformer without the app and just as DAC. I’d give the Transformer another look perhaps.
Depending on your usage you can get close to using it without the app.
You can certainly use it as a DAC. That’s how I’ve got mine configured with my Squeezebox. The Transformer is at 100% volume, Squeezebox connected to it via optical and I control everything through the Squeezebox in this configuration. Once the transformer supports Qobuz I’ll reassess. You certainly need the app to initially configure it, but once configured you can use a button to select input source and it’ll function as a pass through DAC without needing the app.
I can't see how to use the Transformer without the app. The app is needed for monitoring and control.
Another approach would be to rely on Spotify Connect. Again you’d have to initially configure the Transformer, but after that you can use the Spotify App to pretty much do everything just like you do on almost any device. It acts as an endpoint.