Regarding supporting devices long-term, I can still get current version official OpenWrt for the Netgear WNDR3700v2, which I think is about 15 years old at this point.
https://firmware-selector.openwrt.org/?version=23.05.5&targe...
https://openwrt.org/toh/netgear/wndr3700
I always try to find out what's one of the best-supported OpenWrt routers at the time I'm shopping. And can I get one (or a few) of them on eBay at great prices.
WRT54-GL, WNDR3700(v2,v4) and WNDR3800, Netgear R7800.
I also have an OPNsense box that I'm evaluating. But, since OPNsense (FreeBSD) isn't strong on WiFi, I'd need to pair it with separate WiFi APs (running OpenWrt). I'm not liking the extra complexity, when an OpenWrt R7800 still does everything I really need right now.
> WRT54-GL, WNDR3700(v2,v4) and WNDR3800, Netgear R7800.
The WRT54-GL stands out, while having a really long support life it's also just FE, 10/100Mbps. The others are gigabit Ethernet. Could possibly be replaced from the list by the D-Link DIR-825 (N, not AC) which is also at the same support level as the Netgear WNDR3700v2.