Just thinking out loud: could you move the yuzu data folder to a place that Syncthing can access and create a symlink from the original to the new location?
I think the biggest problem would be file ownership/permissions, but otherwise should work.
"Spotify forces you either to pay, listen to ads or to find unofficial, potentially dangerous versions to use it."
I don't think the company forces you to do anything. It is their business model, how they can provide copyrighted music to you and have a share of the pie too.
I'd say the very idea that Spotify is forcing you to pay with time and attention or money so you can have music conveniently streamed to your devices is a testament to the company's success. It created this business model and fulfilled an apparently basic need to the point you think that charging for it is unfair.
But "forcing" is too much. You can always buy discs, digital downloads and so.
Similarly, had a Chromecast Audio powered with USB from the audio device it was connected to. It always whined.
Then I changed it to be powered by the power adapter that came with it. No more weird noises.