Does OpenWRT support hardware NAT? Unfortunately, as you may have guessed, the answer is no. Yep, so that’s why the Linksys WRT AC3200 router that works well with OpenWRT must consume 12 volts at 2.5 amps. That’s the price you pay so that the NAT can all be done in software at gigabit speeds. So, don’t even bother asking if you can have gigabit routing speeds in LibreCMC.
Nevertheless, there were some pretty good attempts to get this project moved forward into mainline OpenWRT.
20200110/DuckDuckGo openwrt hardware nat
20200110/https://forum.openwrt.org/t/hardware-nat-for-lede/1094
20200110/https://dev.archive.openwrt.org/ticket/11779
20200110/https://openfastpath.org/
20200110/https://openfastpath.org/index.php/service/technicaloverview/