I am looking for a router, and OpenWRT came up. I was looking at their table of hardware and the ASUS RT-AC3100 seemed like a good option, as its cheap used, (~$40 USD) and supported by the latest OpenWRT version.
Thing is, its EOL, per Asus. Does this mean that it won’t be supported on OpenWRT for much longer?
Is there a way to see or estimate when a router will no longer work on OpenWRT?


Pretty much the same as any other incarnation of openwrt, just without a lot of the compatibility headaches and weird installation processes that you typically have with other architectures. It’s just install and forget pretty much.
As for the link speed, you can just
cat /sys/class/net/eth*/speedas with any other linux system. Not sure how your configurations stopped working or broke, maybe your storage got corrupted or something? Hard to tell, but I doubt openwrt caused it on its own, it sounds new to me.