Is bonding two lan ports (eth0) possible?

I currently have two WRT3200ACM routers, one acting as a base with a cable modem and a few desktops connected over ethernet, the second router is connected over ethernet to the base router to extend wifi coverage.
With everyone working at home we need more computers connected over ethernet, so I'm adding a switch to hardwire more than 3 devices.
Since I'll have ports free on the base router, I'd like to bond two of the lan ports together to connect the base and repeater router with more bandwidth. If this is possible I'd bond the other two lan ports to connect the switch with higher bandwidth as well.

I've found other posts on bonding eth0 and eth1 (one of the lan ports and the wan port), but is it possible to bond two of the 4 available lan ports (eth0) on the WRT3200ACM? I'd like to keep using luci to manage the network and would like to keep the cable modem on the wan port (eth1)

It is not possible, yet.

Good news is some developers are working on DSA link aggregation offload. So it will be possible in the next release after 21.02.