Since your initial post, I downloaded fresh tomato source code, compiled it and loaded it on an old router and it works. Very simple to do and it took about 20 minutes to compile on an older Core2Duo machine.
Just today and before your post, I'm downloading and trying to compile openwrt to see how it works. Compiling and building the 2, fresh tomato and openwrt, are completely different. Openwrt tries to be more user friendly.
PS. I picked up a Linksys EA6400 for $5. Yes, I know it's broadcom based so I'm limited to dd-wrt if I want 802.11n, ac and 5Ghz, but I thought it was too good of deal to pass up.
I also see another $5 used router that supports openwrt (8MB DRAM, 128MB flash). The current openwrt flash size for it is 3.8MB so there's lots of room for future code. The router and code supports 802.11n and 5Ghz, but the router doesn't support ac.
The reason why so many, IMHO, good used routers are so cheap is that more and more ISPs when they are replacing or upgrading the customer's dsl or cable CPE, the new ISP CPE are coming with wifi/router built in and customers are opting to use them instead of buying new $100 routers that support 802.11ac and 5Ghz.
My old cable CPE didn't have wifi and router functionality. My new cable CPE does support 802.1n, ac and 5Ghz, but I have it set to bridge mode and use my own router as I don't trust the cable provider to properly manage those settings and I have no idea what backdoors are present.
In my area, 80% the broadcast SSIDs are ISP1xxxyyyzzz, ISP2xxxyyyzzz. So many are opting for the ISP routers and they aren't even bothering to changing the SSIDs and default passwords/keys on the front sticker of the CPE.
More on home router security since your initial post.
https://routersecurity.org/