The WRT54GL: A 54Mbps router from 2005 still makes millions for Linksys (2016)
arstechnica.com
arstechnica.com
Fondly remember White Russian on the WRT54GL
https://en.wikipedia.org/wiki/NSLU2
It was a very hacking friendly device. Here's the archived page (the original one is long gone) about hacking it before OpenWRT became a thing.
https://web.archive.org/web/20160313233931/http://www.nslu2-...
This is a good basic model for trying it out: https://www.gl-inet.com/products/gl-mt300n-v2/
It was popular with OpenWRT. What's the 802.11ac 5ghz equivalent now?
TP-Link seems to be a consistently good choice as they have a number of models with a more CPU power and memory than the minimum necessary.
I own two of these and while they now sit in my garage I've probably used them for 15 years. I bought them exactly for the reason laid out in the article - this router has solid hardware and the fact you could out just openwrt/ddwrt on it was amazing.