Hi Folks,
Joined the forum some time ago but this is my first post, or at least I think it is.
My first foray into open-wrt is using a RaspberryPi - so far impressed, using a R-Pi 3b+ and followed an excellent online tutorial.
https://gremaudpi.emf-informatique.ch/create-a-routed-access-point-with-raspberry-pi-and-openwrt/
Got a subnet working fine so now to experiment.
Geoff Lane
Good second start, welcome ;- ) Forum software states:
It’s been a while since we’ve seen Geffers — their last post was 2 years ago.
Welcome back 
Two years ago eh? No secrets here 
Think back then I was looking at flashing a friend's old Linksys router but seemed memory insufficient.
The Raspberry Pi good to learn on, plus being a subnet of my existing network the main network remains stable at all times.
Geoff