Does anyone know if the BT Smart Hub router is capable of link aggregation? The idea of using two Ethernet cables directed to my switch sounds nice to increase bandwidth.

Thing is even if the BT router did (support LAG) it wouldn’t really make any difference to your internet connection as that is < 1 Gbps.

On a network switch if you had for example a NAS connected with multiple Gbps ports arranged as a LAG or a 10 Gbps connection then under heavy usage you would see a benefit with multiple Gbps connected clients simultaneous access to the NAS or a single client (if it also had > Gbps connectivity)

LAG is also useful for inter-switch links or where you are stacking switches.