Static IP, without LUCI, offline

hello everyone,

yesterday I try for few hours seemingly easy thing to do -set static WAN IP from commandline for turning on internet and install Luci ... but with no success
more precisely on wifi router (Archer C6) with no official support = snapshot = no Luci (offline)
used last snapshot squashfs-factory installed with tfpd64 and edit /etc/config/network adding/changing values (putty, winscp) + restart

changed only:

config interface 'wan'
option ifname 'eth0.2'
option proto 'static'
option ipaddr 'XX.XX.XX.XX'
option netmask ''
option gateway 'XX.XX.XX.XX'
option dns 'XX.XX.XX.XX XX.XX.XX.XX'

...sadly all this is not enought

at the end thankfuly I found custom build 19.07 on this forum for this router with Luci... which save my day and more
After set everything from Luci I checked /etc/config/network config and everything was same, but working... I had to forgot set something somewhere else

So, your problem is solved on version 19, correct?

no, thats not the point... point is what more needs to be set thru commandline or editing files for working wired connection with static IP, because WAN config in /etc/config/network is not enought
whats more if I did not found compiled snapshot with Luci then I would have to go back to stock firmware .(

Custom or snapshot firmware?
Those are 2 different terms.

I was asking a question, so I'm not yet certain of the "point" you're making. Looking at your device's hardware page, snapshot is the only currently supported version.

Nothing appears wrong with your WAN config. To see how to use the command line to setup OpenWrt Interfaces, see:

Untrue. See LuCI the essentials page - linked above.