Since I seen a few questions about firmware updates after enabling developer mode, I thought I share, since I managed to do this successfully using seaky’s root tool today
Download and Install the Root Tool
https://github.com/seaky/nspanel_pro_roottool_apk/releases/tag/v1.0
adb install nspanel-pro-roottools-1.0-release.apk
Download the firmware, I found 1.7.0 here and upgraded from 1.5.6
https://drive.google.com/drive/folders/1bHLLJy8vYUjkCCnyUmrHgEFWi_2cxywv
(If anyone has a newer release, please post)
Make file system writable (not sure if this is necessary)
mount -o rw,remount /system
Copy the file onto the NSPanel Pro
adb push <path to file> /storage/emulated/0/system_update.zip
Open the root tool in the NSPanel Pro, click verify and install if the file is good.
This procedure worked for me, but of course no guarentees and to be done at own risk.