Is it possible to connect a flint 2 to a PC via the 2.5G port and have the flint 2 wirelessly connect to the main router to give internet access to the PC. Effectively the PC thinks it's connected to the internet with an ethernet cable but the Flint 2 is connected back to the main router over the Wifi. I hope that makes sense.
Yes, make a wifi client connection and set it up as your wan interface. Double nat here.
Or https://openwrt.org/docs/guide-user/network/wifi/relay_configuration
The Flint 2 seems like a very expensive way to solve this problem. Unless you happen to just have one lying around I would look into maybe getting a network card or a USB C/Thunderbolt solution first.
It is indeed a spare one just freed up by the need to switch back to the ISP router for digital voice.
I was curious what the wifi speed would be using the flint 2 as client VS the onboard wifi on the motherboard in the PC (with external antena). There is a decent improvement but wired is still much better so will look at running a cable. Once I'm finished tinkering with this spare flint 2 it will be sold