Not official answers, but some thoughts from a user / modifier of similar systems.
That’s going to be extremely challenging. If you are okay with the system simply going down during most of the night when you get a stretch of short winter days that all turn out overcast, it might be a little easier than trying to make sure you have enough battery to get through a stretch of low insolation days and then enough panel to recharge it before you get hit again. If using a pi based solution, you need a battery controller that can actually command a shutdown, the openwrt gateways are a bit more robust against unexpected power loss though it’s still not a great idea to do so without warning, particularly if they are running an on-board LoRaWAN server stack (a traditional LoRaWAN gateway reporting to a cloud stack doesn’t have any local network state it needs to preserve, only the integrity of its software to worry about).
- Can I run a local node-red server on the Edge Max as this is possible with the Raspian based D4+?
I would doubt that’s an official capability. Practically, if you can get a compact enough setup and build it with the mt7628 openwrt 15.05 cross toolchain, possibly. But that would be an expert level project entirely outside of the supported, intended use of the box.
- If no.1 is not possible, and I use a locally connected node-red server hosted on a RPi, can I share the Edge Max’s LTE connection with the RPi?
In theory the openwrt operating system can be configured by an expert in that to do this (it’s meant for routers after all) but I don’t know that it’s offered as an intended and supported capability of the gateway product. I’d probably put the modem on the custom system instead and have it provide an Ethernet connection to the gateway. But two computers are going to increase your power consumption and the number of places where something can go wrong.