I’ve got an R3 at home which generally works well. Flashing mainline OpenWRT was pretty smooth and easy. It’s been a while since I did the bring up, but I do remember having to jump through some hoops to get a partition layout that would utilize the onboard storage properly. By default it only left 10mb to install additional packages which seemed to defeat the purpose of having all of that emmc available. That may have changed in the more recent releases.

One bug I encounter regularly is that some (maybe older?) Apple devices seem to be able to lock up the router. Adding watchcat can get the thing rebooted in less than a minute in the event that it does hang, which makes it barely noticeable, but it’s not an ideal fix.

Depending on the devices you have in your house that might be a showstopper or of no consequence at all. Otherwise WiFi speeds and signal are great, as are general performance and reliability except for that bug I mentioned. Haven’t used VLANs but it’s all there and the flexibility of OpenWRT is great.

You might be able to get by with the power supply but 750+ watts is recommended for a 3090. Any B550 motherboard should be totally fine.

For what it’s worth I’m running a 5950X, 3090, a pair of water pumps, and 11 fans all off a 750 watt Corsair PSU and I’ve never experienced any instability or signs of an insufficient PSU.

If it were me in your situation, I’d just pick up a decent 750-800 watt PSU, and upgrade the memory to a decent 32 gig memory kit while I’m at it just to have a little better time. 3600mhz with decent timings seems to be the sweet spot. Otherwise, as long as the GPU fits the case, you should be in great shape to run it.

Wow, I’m jealous you live somewhere that you can downgrade to 2.5Gb/s!

If you go that Banana Pi route, just be aware that the process of getting mainline OpenWrt on the thing is a little unusual, but not difficult at all. Just requires a cheap serial adapter and spare micro sd card.

There device has onboard NAND, NOR, and EMMC, as well as the card reader. Not all can be used simultaneously, so there are dip switches that set what is booted/visible.

Official install method is basically as follows:

-Hook up serial adapter to the send/receive/ground pins on the board, open serial terminal in something like PuTTY

-Set dip switches, boot the sd-card

-In serial terminal select option to install to NAND

-Power off, change dip switches, boot to NAND

-In serial terminal select option to install to eMMC

-Power off, change dip switches

-You’re done, now booting mainline on eMMC

Basically just putting the image on the NAND memory temporarily so it can be put back on eMMC since eMMC and sd-card can’t be used at the same time.

The Banana Pi forums are a good resource in addition to the OpenWRT docs.

My only gripe at this point is that the mainline configuration by default only sets up a 100mb partition on the eMMC to install packages to. Some folks have had success resizing that partition but I wasn’t having any luck there, so I may just compile it myself and set it larger. That change should be persistent through system upgrades after it’s done once.

Anyway, if you or someone reading this goes that route, I hope this helps!

Check out the Banana Pi BPI-R3. It’s getting mainline OpenWRT support with the 2023 release (RC builds available now). Amazing performance to price ratio. The only thing on your list that might be an issue is the 5Gb SFP. It has two SFP cages but I believe they max out at 2.5Gb. Also recommended to get the bundle with case and antennas included. Amazing price for what you get.