LuCI - client side html vs server side html

Hello Community,
I have recently started working on OpenWrt platform and trying to understand OpenWrt Web Interface LuCI. I have come to know by now that LuCI is generating the html pages using LuCI JS APIs in the browser.
My query is - Since what version of OpenWrt, LuCI is following this pattern and is it possible to write the a web application with server side template code for html page with the latest LuCI web interface and if yes, how can work with this hybrid approach. Any documentation reference is highly appreciated

Thanks,
gargsa