I don’t need super performance out of the wifi, just basic connectivity.
I could use a Map-lite for wifi-only, but would avoid if possible to save on the power budget.
I very much would like to find any USB dongle that would work. Maybe something AR9300 based? anyway, has anyone tested something that worked?
There is no wlan on usb support in any current mikrotik version.
You will have to buy one that have all your required wireless options.
But if you only need more LAN ports and your chosen mikrotik board have USB, you can use USB to LAN adapter.
Even the cheap ones from Aliexpress (black with two LEDs) work quite well, can reach about 80MBit/s and appear as new interface in mikrotik.
I haven’t tried plugging more than one using USB HUB, but that might be possible too.
So maybe you can solve your problem by inverting it: buy device that fits your wireless requirements and then add LAN ports over USB…