Im considering purchasing a Banana Pi OpenWRT router.
My previous devices have all had internal aerials but this device has four connectors.
Knowing almost nothing about Wifi 6 and aerials How feasible is it to run extensions from one or more of those aerials out the wall of our house and use a larger uni or directional aerial to extend coverage in a particular direction from a high point or should you always have the same short aerials that come with the router?
You won’t be running an additional router. If the WAP you use has a router function, disable it. Searching the openWRT docs for ‘dumb AP’ should put you in the right direction.