Generally good advice, of course, but I don't think it applies in this case. I checked before I wrote the dremel comment, and I'm pretty certain it's a two-layer board. I don't have an x-ray setup handy, but all of the vias that I can see come back out the other end.
Though your advice still stands, regardless: If you can't be sure, don't take a dremel to it. And if you do, know that you do so at your own risk.
As I've said: Won't defeat the microphone for certain, might just muffle it. Could be sufficient, but might not be.
This will break your streaming capabilities as well if you block the entire device. If you block just the right ports, you'll have to figure out which ones to block first, and hope that they won't be used for any other functionality the device might consider "crucial" for its operation.
And just to clarify:
I'm not arguing against any of this. It's all very good and solid advice. All I'm trying to say is that I don't understand why anyone would buy this device in the first place. If you don't have a good reason to trust the manufacturer to be honest with how they use the microphones that they ask you to install all over your home for them, and if you can't really reliably defeat those microphones without running the risk of bricking your device, then don't buy their products.
And this doesn't just apply to this particular manufacturer of audio and TV streamers that just so happens to be Chinese, it applies to everyone, including Amazon, Alphabet, Meta, Apple, and pretty much all car or "smart" phone/watch/speaker/door bell/TV/younameit manufacturers.
Apple has earned my trust to a sufficient degree with how they generally have been acting over the past decade regarding user privacy questions, which is why you will find their products in my home. Alphabet has proven to be a shady actor in this field at best, and Meta and Amazon have made abundantly clear that you can't trust them at all. So you won't find any hardware containing a microphone or camera from them in my home, period.
WiiM/Linkplay is an unknown actor to me. They might have the best intentions, but they haven't proven that they can be trusted, either. And until that changes, none of their products will remain switched on unattended for any length of time.
I'm not a tin foil hat kind of guy. To the contrary, actually; most people will probably describe me as rather naive and maybe a bit too trusting. But when it comes to this kind of stuff, I might have spent a little too much time in this industry to blindly trust some random manufacturer with their declared intentions by installing hardware in my home and place of work (where I regularly discuss trade secrets that are in part covered by NDAs) that can easily be converted into a sophisticated surveillance device with just a small, automated over-the-air firmware update behind my back.
Edit:
I will remove myself from this discussion now, if that's ok. It wasn't my intention to have this turn into a WiiM dissing session. Sorry about that.