After I installed Lyrion Music Server on a Linksys MR6350, I had been thinking of adding squeezelite to the router to act as a music player. For that purpose, I need a 2nd USB port on the router for the audio DAC adapter. So when I got my hands on an old Netgear R7000, I tried to install the LMS container on it but it failed to run with an exit code '132'. Some googling told me that the code could be related to execute unsupported CPU instructions. It turns out that the R7000's CPU is armel (ARMv7l without hard float) which LMS docker container (and non-container download packages) doesn't support (arm64 and armhf only). I know there is a possible alternative - running debian and LMS in the OpenWrt chroot environment. It so happened that I had compiled an armel CPAN 3.36, which was needed for a Pogoplug PogoE02 to run LMS in debian bookworm. Now all I needed was to figure out how to setup the chroot environment. Well it wasn't that technically chanlledged following the [OpenWrt Wiki] CHROOT guide. I did have to setup extroot first (a 500MB partition) because R7000 has only 18M flash space. In the debootstrap step I made sure the arch=armel to get the debian bookworm base kernel. After installed the LMS deb package (lyrionmusicserver_9.0.1_amd64.deb and dropped in the armel CPAN 3.36 into the right place (//usr/share/squeezeboxserver/CPAN/arch/5.36) and issue command 'service lyrionmusicserver start' at cli, I had LMS running. Did a reboot to make sure every was fine and it was. (The only inconvience is I have to get into the chroot environment and run the "server lyrionmusicserver start" on every boot.) I then installed the OpwnWrt "squeezelite-full" packgage (some setup required) and now I have a music playing router! I am listening to the music from the R7000 while I write this post. 
Music codecs in general are float based, you have to have fpu to decode music.
Which also means you have to use armel packages in your debian container, certainly not arm64 ones.
Your issue is about debian armel and stuffing incompatible packages onto it. Get arm64 router for your music or use purpose built streaming device like your mobile phone.
Just a suggestion, but what about a x86_64 based (not older than AMD T56N or Intel baytrail/ cherry-trail, roughly 2011/ 2012 or newer!) thin client instead?
- small
- silent
- ethernet
- onboard audio ports
- 2-8 GB RAM
- disk size is a bit on the low side, in the entry level you see 2 GB, 4 GB, 8-16 GB if you're very lucky, often mSATA (sometimes NAND/ eMMC), sometimes with an additional SATA port
- USB ports (USB3, if you're lucky)
- onboard (client-centric) wireless cards are possible/ available on a few devices
- power consumption varies between devices, with good choices you may be in the ~5 watt range, worse ones around 15-20 watts
- prices ~10-25 EUR for the older/ entry level devices
- on the face of it, these are low-end, but normal x86_64 systems - only limited by their system specs (so mostly disk size)
see e.g.:
A good rule of thumb would be not buying anything older than 10 years (that alone should have disqualified the r7000, Broadcom should have been the next red flag; x86_64 and UEFI should be on your must-have list). Favour 'complete' offers (including PSU, RAM, disk), as buying a compatible PSU separately might cost just as much as the thin client itself (so complete offers are likely to end up being cheaper). mSATA or SATA DOMs are getting exotic these days, so extensibility is a bit limited (at least as long as you keep it sensible, a lot of things are possible, but way fewer are economically viable). From an economic point of view, I would advise not going into it with a plan to 'just exend it' - take your time to find a device with comfortable specs.
USFF devices from the big four (Dell, Fujitsu, HP, Lenovo) with i3/ i5 (haswell and newer) are starting just above the price level of these thin clients, so you might find a good bargain there as well (RAM and disk are easier to extend there, respectively are likely to be at comfortable levels to begin with).
This is just a suggestion for cheap/ low-end devices, the sky and your budget are obviously the limit.
EDIT: if you already own a NAS or similar devices, virtualization/ containerization might be an option as well.
I fully agree with your points of a high-end device for media playing. I do have another couple of routers (Linksys EA7500v1 and Netgear XR500 with two USB ports but until I put the Linksys MX4300 into service and replace one of them, R7000 will be the device to bridge the gap.
Those would be easier, in the sense that they're normal ARMv7/ armhf, without nasty surprises (and fully supported).
I bought the R7000 used probably 10 years ago. It so happened that it is there when I looked for a spare router with two USB ports. My purpose is a device that services multiple functions and with min. foot print. R7000 is configured as DumbAP to add extra lan ports (needed for a wired-only "old" HP laserjet printer and a VOIP phone adapter), functions as OpenVPN server when I travel, provides music storage for sharing and lastly a music player. I tested out its performance and noticed that the router will be dropping packets because of bandwidth saturation. But I think it would do because I only play music when I am home and will turn off LMS when I travel and need OpenVPN.
Yes, I encountered a lot of unexpected surprises on the way. But don't really mind the extra time to work it out and learn a lot of new things (to me) on the way. Now my next idea is to find some way to run LMS directly under OpenWit? No docker container or chrooted debian. I actually had tried to complie the LMS CPAN module under OpenWrt but went no where. But I haven't totally given up yet.
The router can not decode sound. You can make it a speaker like streaming decoded stream.
Why not? My ASUS RT-AX53U is a perfect audio streamer with squeezelite and USB audio.
That is why I want 2nd USB port to plug in a digital-to-analog converter (DAC) adapter so that I can play sound. I know there are USB video adapters. With Debian running under the chroot environment I wonder if R7000 has the capacity to display something.
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