I can't give you first hand confirmation of an adapter that works with the ONN 4K Stick (2026), but this is the first one I would try:
https://www.amazon.com/right-angle-usb-c-ethernet-adapter-fire-tv-stick-hd/dp/B0F14YX5TG
I know it seems weird that it's for a FireStick, but at least one review reports that it works with other streaming sticks that use USB-C. The right-angle adapter is a nice touch.
It's actually quite nice, thanks! If they stop supporting Ospreys, I'll probably go more in that direction!
I just wanted to report back on this since I bought three of these, and unfortunately, they do not work with the Onn 4K Plus. They might work with the Onn 4K stick, but unfortunately, I have three of the pluses, so I will have to use Wi-Fi. It seems like all pass-through Ethernet adapters don't work.
What happens is it does work initially, but the moment you turn developer options on and enable USB debugging, it kind of breaks Ethernet upon reboot. So it's not really a sustainable solution. It's best to just keep those boxes by the router and hope for stable Wi Fi.
Yeah...I got an onn puck and that can be challenging to get ethernet working. You have to disable usb debugging, reboot and put it on again.
Firetv works almost out of the box
My setup uses Xfinity as a source. Fortunately, my cablecards are still working at the moment.
However a few years ago I set up the firestick option to replace my Windows Media Center as a way to source premium channels for my DVR. I use basically the setup you describe, with the exception that I use ah4c, not ADB tuner.
The Firesticks are connected to a 4-port HDMI encoder. Therefore I can expand it in the future. Currently I have two Firesticks connected. They access the Xfinity streaming app. AH4C controls the tuning, and Channels picks up the output from the encoder.
If you also have Xfinity for your home internet you'll avoid some issues that I have. A couple of the premium channels are not accessible via streaming to me, since I don't have Xfinity Internet. However most of them are available. One advantage of streaming is that standard definition premium channels on Cable come through in high definition on streaming. There are occasional exceptions where aspect ratios get wonky but that's rare.
The reliability is a lot better than Windows Media Center was. I played with ah4c's captioning, a recent feature, but turned it off. I find that I haven't yet figured out how to tune that part of the configuration.
Regarding your cable cards, Xfinity has a website you can use to activate and pair your cable cards to your device, so you don't need to talk to a person. I'm guessing you've already know that.
Which firestick is the one to watch out for if I were to stock up on Prime Day? Just in case the Ospreys die soon lol
Any of them could do but I would look to get one with the most space which is the FireTV Cube. Some of those Cubes can be bought as an open box on ebay for a hundred bucks. I won't be surprised if there's a newer model coming in around that time but it may not be android based
Yeah I'm looking for what can tune fast for as little money as possible lol. I'm curious how the 2026 Onn 4K Sticks compare to the Plus. If those drop in price on black friday I'll probably start hoarding them.
Why are folks so concerned about tuning speed? Do you still channel surf?
Yes! I watch mainly live.
Gotcha. We stopped watching live TV about 15 to 20 years ago as we realized the advantages of the PC DVR (with comskip). To each their own I suppose.
I mean things like cable news, sports, etc aren't too relevant after the fact.
We watch all of our news, sports and etc. about an hour or two behind the actual recording. It took some real convincing here at Channels DVR, but to the credit of the developers, they eventually they figured out that live comskip can actually work to some degree, and the user doesn't have to watch all those ads. On the other hand, if the user can't wait an hour or so, I completely understand.
I may pick one of those up in the am. It's no more expensive than a 4K Max after trade in.
I’ve got the older 4K hockey puck style as a 3rd tuner for my FDL/AdbTuner stack and it works okay.
Let me know how it works. I still prefer the Ospreys but I want a backup plan and given my Fastchannels PR getting merged and proper DTV channel numbers inbound that is a viable solution for me if I needed to go that route.
I haven’t turned the Osprey's off yet but have FC set as a higher priority. My tuning speed is about 1 second less than Channels TVE.
I'm hoping there's a nice easy way to add a tuner. 
I wouldn't know. I could have written perhaps 10000 lines of the code with my robot buddy to maybe probably make a tremendous webui.....
A couple of notes on the ONN 4K Stick (2026):
It's a touch slower than the FireStick 4K Max (Gen2)
It has half of the app storage capacity
It does not have WiFi 6 at all, much less the WiFi 6E of the FireStick (potentially an issue for sticks in a tight pack using WiFi)
Compatibility with OTG Ethernet adapters is unknown at this point
I have two of these sticks in my test setup, and they seem fine generally. I prefer the FireStick 4K Max, but they're my next favorite -- mostly due to their similar form factor.
EDIT: Forgot to mention, they do have the dreaded "wireless pairing" of Android 14. However, you don't need (or want) to use it. Just the usual Developer Options, followed by enabling USB Debugging, and they can be ADB authorized -- including that authorization surviving reboots.
I'll aim for those then, just have to wait for a price drop!
Thanks for the info. Unfortunately the CableCARD website no longer activates cards. The message says to call Xfinity, but so far none of the reps I've talked to knows how to activate a card. I've purchased the hardware to switch to Fire TV Sticks + LinkPi + ah4c. I've got the sticks and ah4c setup, just waiting for the LinkPi to arrive in the next few days. Constructing an m3u for my channel lineup has been more work than I expected. I thought there'd be a Schedules Direct-type site that already had Xfinity streaming deeplinks cataloged, but it looks like that's a manual process. If you have a good Xfinity m3u you're willing to share, please do so in the ah4c post. The m3u on github is fairly small and missing a lot of channels.