The Linksys 1900AC router was released to the public as a great option for people who wanted to have a top notch router with support for open source firmware. Now that some time has passed there is now alternative OpenWrt firmware (Chaos Calmer) available allowing a finer degree of customization then the factory default firmware.
After installing the latest firmware (at your own risk), you will then want to add the LUCI GUI interface.
opkg update
opkg install luci (or luci-ssl for https access)
/etc/init.d/uhttpd start
/etc/init.d/uhttpd enable