So I rolled back esp-at to 8th May and that caused errors in atUnified and atWiFi. So I rolled those back to 8th May as well and finally it worked. Thanks @Dennis_Mabrey for the pointer in the right direction - I’m very pleased my brand new Wio Terminal can now connect to wifi.
16:40:41.143 -> Connecting to WiFi..
16:40:41.650 -> Connecting to WiFi..
16:40:42.158 -> Connecting to WiFi..
16:40:42.669 -> Connecting to WiFi..
16:40:42.669 -> Connected to the WiFi network
16:40:42.669 -> IP Address: 192.168.1.107