Hardware recommendations for sniffing WiFi traffic?

I'm doing IoT device development work and I don't have a good, reliable way to capture WiFi traffic. Wireshark doesn't show my WiFi network interface on my Windows development system, and sniffing WiFi traffic on my Ubuntu laptop causes the network connection to drop and sometimes also crashes Wireshark.

For now, at least, I'd be satisfied with capturing traffic off the wired side of the network. Ages ago, when I was a sysadmin for a 3000-user site, we had managed switches with monitor port capability - and before that, dumb hubs. What I have now is very little budget for extra hardware and an office with consumer-grade network gear - a Linksys E2500 and a handful of other access points, bridges, and unmanaged switches, none of which have any kind of port mirroring.

I'm really hoping to avoid standing up another Linux box that I have to maintain, and try to remember how to configure. Can someone recommend a reliable access point / router with port mirroring? Or a dedicated tap device?

There's also stuff I will need to capture off the air eventually, since the Silicon Labs WiFi modules we're using are full of weird quirks and bugs, so I'm open to recommendations for wireless capture hardware that works reliably with Wireshark.

I'm way out of date on some of this stuff, short on time, and the signal-to-noise ratio for all of the Google searches I can think of is awful. It's 2018 - there ought to be a cheap off-the-shelf solution that just works. Can someone point me in the right direction?

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Thanks!