Tangential but on the topic of IP routers - recently my EdgeRouter X died. During autopsy, heat deformations were found on its Flash right next to an inductor for input DC-DC circuit.
So, naturally I hopped onto a train and bought a used NEC UNIVERGE IX2105 to replace with; a compact, fan-less, half A4 sized sheet metal pizza box with blue accent on matte white. Functionally a Cisco ISR 892J or 1941, physically smaller. Current models in its siblings range from ~$750 to $2.5k, however this Model 2105 is no longer officially supported, and are sold cheap in used market($30-50). It still has one GbE and one integral 4-port L3 switch, with up to 440Mbps advertised VPN throughput, an Apr/2022 built firmware, and full support for IPv6, OSPF, BGP, etc(that shamefully I had failed to understand).
I suspect it runs BSD in some shape or form as `show copyright` command shows licensing terms for FreeBSD and BSD library among others, but it won't let me drop into shell, nor does the typical *nix daemon parade on boot. The CLI is basically a Cisco, or like VyOS/Ubiquiti, except there are no obvious telltales of dancing bash contraptions and required facade massaging, unlike with many Linux-based routers. Firmware files for its lineage are also extremely small by modern standards(~8MB), RAM sizes are small too(16~128MB).
It does its things, and does well. A downside is it's proprietary. I used to run OpenWRT in 11b/g days but I suspect that was before it incorporated a unified config file. I was obviously on VyOS/EdgeOS until last week, and while it had served me good, it did trip over stones once in 2-3 years. I've also heard RouterOS is great but stable as Stable build bricking itself. I've used OpenWRT but that was before iPhone and perhaps before it even had a unified CLI configuration. Is OpenWRT better in stability/footprint/simplicity these days?