Mini Appliance & WLAN AP

Concerns IPFire Mini Appliance > WLAN AP settings. Core 166 & APU4 updated. HW Mode 802.11an. HT & VHT caps same as last year. Sales information appears to represente WLAN can operate AC mode. Yet when tested the AC mode doesn’t connect. Is that a limitation of the mini WLAN and therefore mode AN is best?