The brightness might just need a little burn-in, but distortion will never settle in. Is it possible you have a damaged unit (with the body panels not flush, etc.)? If it’s not been assembled correctly it might be rattling at high volumes which might sound like distortion…?

If your dealer is nearby, maybe it might be possible to compare it to another, or their demo model, to see if this is a general issue or confined to your unit. Honestly, I would want a replacement on build quality alone from what you’ve described.

The other app issues are a shame, but presumably fixable in software/firmware. Or, if you can get to the bottom of the brightness/distortion/build issues to the stage where you’re happy to keep the unit, Roon is really excellent, especially from a wired Ethernet connection.