Interestingly enough, MikroTik routers are mostly well supported by OpenWrt it seems. At least that's what my search for something that is beefier than regular OTS Routers has yielded. Flashing OpenWrt is a little cumbersome though.

TP-Link, the former manufacturer of my choice, unfortunately has become a version roulette it seems.

If power consumption does not bother you, maybe banana pi? Or something atom based?