Yes, the situation is indeed ISP-dependent, unlike an audiophile switch. It seems like we’re left with little choice. Manufacturers of filters, switches, and routers will likely continue their development for years to come, but I’d rather not invest any more in achieving a noise-free upstream for cleaner output at the DAC.
Maybe of interest for you in potential features of an audiophile router, I’d like to share the Ubiquiti EdgeRouter ER-4 here and noticed that Afterdark has modified it into a world premiere clocked audiophile router.
The MikroTik CRS305 router/switch has been discussed on this site as well. However, it still relies on different ISPs and the routerOS requires programming skills that I don’t possess. I’m already curious about the potential benefits of swapping SFP modules in the Fritzbox, but I acknowledge that again this might divert attention from the core issue.