TL/DR version is: you don’t. Use external AP with vendor-provided firmware to get stable and performant WiFi.
Long version: In general decoupling things like central network mini-servers/routers and disposable infrastructure elements like WiFi APs is a good idea. WiFi protocols get updated and WiFi security gets patched at a way faster pace compared to the speed upgrades we get at wired networking space. R2 is performant enough to be able to satisfy my routing and home server needs for approx 5-6 next years. On the other hand I had updated my 802.11n AP to 802.11ac AP in the end of last year and it is already sort-of obsolete as WiFi 6 (802.11ax) is on its way to public.
But even leaving this aside the built-in WiFi chip in R2 is known to be “brittle/tricky”: there are no upstream linux drivers for it, vendor-shipped drivers are buggy, AP setup process is non-standard, e.t.c. So better bet would be to get a mini-PCIEx WiFi module with a WiFI chipset that is known to be well-supported under linux and try your luck with it. I’ve seen reports on other forums of people having good results with external WiFi mini-PCIEx modules under Armbian. Try checking Armbian download/FAQ page for BPi R2 for more info.