I'm actually just about to replace my 6-year old RT-N66U - the Merlin firmware I use (based on Asus's FW) dropped support [updates] for the N66U a long time ago

I'm actually just about to replace my 6-year old RT-N66U - the Merlin firmware I use (based on Asus's FW) dropped support [updates] for the N66U a long time ago, and the flash process for DD-WRT seems sketchy. The Asus official firmware is missing some advanced features that I need, so doesn't help even if it is getting updates. I looked into making my own router (actually stumbled across your writeup a few times), but didn't want to mess with ARM boards - they have limitations with the speed of connected network interfaces (ethernet/wifi), and just seem complicated to deal with. I researched making a x86 system, but the price would have been ridiculous. I haven't purchased it just yet, but decided on the Linksys WRT1900ACS router. It runs OpenWRT, which is a full blown configurable Linux system (even has a package manager). But installation and updating is simple and straightforward. OpenWRT obviously isn't officially supported, but Linksys and OpenWRT seem to have some collaboration going on. At the very least, they don't program any 'protection' from custom firmwares into the router, and the SoC runs well off of free software (as opposed to many routers which only work with DD-WRT due to needing proprietary Broadcom drivers). The OpenWRT configuration web interface seems 'good enough' to let you set up 99% of use cases easily, but it's just a normal tweakable Linux system underneath. At $160 the router is a bit on the expensive side given the hardware, but the great compatibility with free software is worth it IMO. However, I discovered that the WRT32x (gaming-skinned but hardware equivalent to the much faster WRT3200 [1900/3200 are combined 2.4GHz and 5GHz bandwidth]) is available from multiple sellers on Amazon for the suspiciously cheap price of <$130, so am going to buy one next week when I'll have time to set it up. Side note: The cheaper TP-Link Archer C7 is another popular router for custom firmwares, but installing on the latest hardware revisions is not as straightforward, and the hardware is much weaker than the Linksys ones: https://openwrt.org/toh/linksys/wrt_ac_series https://openwrt.org/toh/linksys/wrt_ac_series. Aside from that I haven't found any good-performance FOSS-compatible routers, except for a D-Link one which compares unfavourably to the WRT1900.