In addition to the excellent advice you've already been given I have two more comments.
Besides the streaming services, I see that there are also radio stations available. Any of them that broadcast in good audio quality?
The WiiM Amp Ultra directly integrates a number of Internet radio stations (like e.g. the excellent streams from Radio Paradise in losslessly compressed CD quality).
In addition it also provides its own user interface to the aggregation services TuneIn and vTuner (which do not support lossless, the maximum quality finally depends on the station).
The third option is called "Open Network Stream", where you can manually enter and manage as many streaming URL as you can obtain for radio streams of your choice.
Is it possible to set it up so that my subwoofer is only active when I’m watching TV via HDMI ARC, and not when I’m streaming music? (automatically)
As pointed out by
@Djinn206 and
@Wiimer, presets can do the trick. There are two limitations: 1. It's not really fully automatic. 2. When the WiiM Amp Ultra switches to HDMI ARC via auto-sensing it doesn't respect any preset (you could store 12 presets just for HDMI ARC with different settings, so which one would be right?). In this case you still had to select the smart preset to switch off the sub.
Auto-sensing can be disabled, but in practice this is a delicate topic and in my experience it hardly works, also depending on the TV model. Also, the convenience provided by auto-sensing is something to get used to fast, especially if the whole family is using the TV and amp.
My question is: Why do you want to disable the subwoofer at all when watching TV? Is it to save energy (in this case I have no better proposal) or just because you don't want the same amount of bass as when listening to music? In the latter case there's a very easy solution.
More or less bass is really just a matter of tone controls or their modern times ancestors, EQ settings. You can assign a different EQ setting (either graphic EQ or parametric EQ) to each input individually. If you want less bass with the TV, simply don't touch the sub setup but assign a saved EQ setting with reduced bass output to HDMI ARC.
This does work automatically.