Will Chanalyzer detect Wi-Fi 6 (802.11ax)?

Yes, as of 5.11 Chanalyzer will detect and display 802.11ax networks and data rates using the WiFi adapter built-in to your laptop.

From a spectrum analysis perspective, Wi-Spy DBx will be able to catch any 802.11ax activity simply because it operates in the 2.4 and 5 GHz bands. More info can be found here.