Is it possible to install lede on a mr3420 v2 with USB 3g dongle support?

Installing and Using OpenWrt
1

I would like to use lede in my mr3420, the main reason is to use a USB 3g dongle..

I've read that 4 mb ram devices are not ideal, but is possible.

So would lede work on my router? And if so what would I need to do to make it work?

2

Use the custom firmware i.e GoldenOrb http://ofmodemsandmen.com or PULPSTONE http://pulpstone.pw

One thing for sure, the firmware should be include block mount kmod-fs-ext4 kmod-usb-storage (extroot). Check this out https://wiki.openwrt.org/doc/howto/extroot