Yes, I provided a detailed explanation of the IPv6 toggling workaround. I hope that detailed examples like that would be helpful to someone trying to debug this, but I've received little/no confirmation or acknowledgement from Wiim that they are even reading my statements, let alone using the information.
Thanks for the confidence but not sure I deserve it!
I'm definitely no IT wiz, but have basic context and aptitude to at least approach things rationally. I do have a little debug background, unrelated to networking, but the concepts still apply (isolate the fault, change one variable at a time, etc).
My router setup has total default from-the-factory settings. I think my Wiim media server setup *should* work out of the box, since my network system is pretty mainstream: Netgear router, no third party firewall or other weird stuff, Pixel phone(s), etc, etc. That said, I recognize that networks are finicky beasts, and I wouldn't doubt that one little configuration detail in Android, or the router, or the Wiim app could throw things off. I just wish Wiim could find it!
I tend to agree that it may well be an App issue. I have noted in the past that I was able to use VLC to find the Wiim media server even when the Wiim App could not, and even play that content to the Amp as a renderer selected from VLC. I've also share those examples on my Wiim ticket, fwiw. But recently I haven't been using VLC in the interest of keeping the network simpler and minimizing other potential disrupters.
The IPv6 toggling thing + the ability to find the media server from third party apps is a pretty strong scenario to provide context for Wiim, I would think. I've been playing with a handful of configuration options on my router (one change at a time) and had some change of behavior, but its really hard to correlate if the USB server shows up due to a change I made, or just because its intermittent/temperamental nature decided to light it up.