This app was mentioned in 4 comments, with an average of 1.00 upvote
Static DHCP / Address Reservation via MAC on your DHCP server is probably the easiest way to ensure network settings on a device.
> I don't have dhcp server available and I need also DNS addresses to setup statically.
Can you elaborate on this? It might be easier to gain access to the DHCP server.
For startup stuff, have you looked into init.d scripts? I don't know if that's a thing with Lineage any more. I used a program Boot Shell (now removed) in the Play Store to run scripts after the system booted to force settings using getprop & setprop. I don't know the best way of doing that now without init.d support or some program that runs scripts after boot.
Yes, best would be if this week to be integrated into the ROM. Ask the developers.
Apart from that, you can run the command on each boot. There are multiple ways to do this. One of them is using an app, like: https://play.google.com/store/apps/details?id=com.kislay.bootshellcommand
gsm.sim.operator.iso-country=gb is a huge pain in the ass.
I tried to make something that forced +1 instead of +44. The script I made relies on your device a) being rooted, and b) has the ability to run scripts on startup.
Source: https://github.com/BitingChaos/android_country_code
My page on it: http://xenomorph.net/google/android/hangouts/
A simple app to run scripts (99¢): https://play.google.com/store/apps/details?id=com.kislay.bootshellcommand
You can use an app called Boot Shell to run the command at boot.