I keep looking into it and keep stopping at 'what should I buy'. I'm willing to / assume I need to buy new hardware. What do I buy that will run it well, and continue to?
This build gets ~750 mbps NAT speed as opposed to vanilla openwrt, which is around ~300 mbps.
It is fair mentioning that this model is discontinued from TP-Link and you will probably have to buy it second hand. It also comes in at least 5 revisions, with various levels of support, making life a little bit more difficult for the average, uninformed buyer.
As a side note: I have a 350mbps symmetrical FTTH link and I've had no issues maxing this line with regular, official OpenWRT builds.
Unless you need significantly higher speeds and can prove that official builds can't do it, I see no reason to go with unofficial, unsupported builds.
As long as you have enough flash to install the modules, I can't see why this shouldn't work on any router.
That is, can I just buy from Amazon [0] with a fairly safe assumption that a new C7 is OK?
[0]: https://www.amazon.co.uk/TP-Link-AC1750-Dualband-Zertifizier...
Consult the openwrt table of hardware[1] for more details.
[1] https://openwrt.org/toh/tp-link/archer-c7-1750
Edit: eBay seems a lot better for this task - https://m.ebay.com/sch/i.html?_from=R40&_trksid=m4084.l1313&...
And it was flakey as f*ck. It rebooted itself roughly once a day, and would stop routing traffic to my fibre modem and need manually rebooted at least once a day.
The Openwrt support forums were... not helpful.
All this was such a shame, because the Openwrt feature set is so much capable than the stock firmware - I so wanted it to work, but had such a bad experience I haven't gone near it since and it will likely stay that way.
Throughout my time I've bought around 2 or 2 routers with the naive assumption "oh it will probably work out fine", and that's definitely not how it works. That has certainly left me with disappointment.
IME it pays off greatly to upfront research the specific model (and revision) and buy exactly that. Like in this case, the Archer C7 v2 (of which I've recently bought two).
It's running OpenWrt flawlessly and I would have zero issues recommending that particular model to anyone.
Strangely, the C7 I have now advertises itself as 'v2/v3'!
I can tell you what I did, which may or may not be helpful to you. I got Linksys WRT AC3200[0]. The "AC3200" bit refers to a type of wifi 802.11ac configuration that has a theoretical bandwidth of 600 Mbit/s using the 2.4Ghz radio (good for distance and passing through interior walls) and 2.6 Gbit/s on the 5Ghz wifi radio. This is not the fastest or fanciest of the 802.11ac configurations, but it's up there.
One note about the marketing of this device, the MU-MIMO feature that you may read about is not really a thing yet. I don't have any devices that support it, and it's possible I never will.
Disregarding the radios entirely, this device can easily push 1 Gbit/s over the the ethernet ports, and can easily exceed 800 Mbit/s using the up-and-coming Linux kernel based VPN WireGuard.
This device is supported by OpenWRT, but if you don't want to compile and build it yourself you need to get it from a helpful guy on the net who maintains community builds for this router[1] and related chipsets. Support is available through a community forum[2].
I'm quite pleased with this device and firmware setup. I like that it can interface with my switch to sort out VLAN tags, I like that I can run cutting edge VPN software like WireGuard on it, I like that it's reliable and I haven't hard to reboot it randomly to "fix" it.
[0]: https://www.amazon.com/gp/product/B01JOXW3YE
[1]: https://davidc502sis.dynamic-dns.net/releases/#3200acm
[2]: https://forum.openwrt.org/t/davidc502-wrt1200ac-wrt1900acx-w...
https://www.flashrouters.com/linksys-wrt1200ac-ddwrt-router
No need to install DD-WRT yourself, just pay a little extra and have it shipped to you pre-installed.