hostapd.conf

--- default:: hostapd-etsi-vht80.conf
driver=nl80211
logger_syslog=127
logger_syslog_level=2
logger_stdout=127
logger_stdout_level=2
country_code=DK
ieee80211d=1
ieee80211h=1
hw_mode=a
channel=52

ieee80211n=1
ht_capab=[HT40+][LDPC][SHORT-GI-20][SHORT-GI-40][TX-STBC][RX-STBC1][DSSS_CCK-40]
vht_oper_chwidth=1
vht_oper_centr_freq_seg0_idx=58
ieee80211ac=1
vht_capab=[RXLDPC][SHORT-GI-80][TX-STBC-2BY1][SU-BEAMFORMER][SU-BEAMFORMEE][MU-BEAMFORMER][RX-ANTENNA-PATTERN][TX-ANTENNA-PATTERN][MAX-MPDU-11454][RX-STBC-1][MAX-A-MPDU-LEN-EXP7]

interface=wlan2
ctrl_interface=/var/run/hostapd
disassoc_low_ack=0
preamble=1
wmm_enabled=1
ignore_broadcast_ssid=0
uapsd_advertisement_enabled=1
auth_algs=1
wpa=0
ssid=5G-DFS
bridge=br-lan

***
802.11ac may have one of three lengths: 3,895 bytes, 7,991 bytes, or 11,454 bytes.
but hostapd accept only 7991 and 11454.
[MAX-MPDU-7991]
[MAX-MPDU-11454]

The maximum length of an A-MPDU is controlled by the value of a field called the Maximum A-MPDU Length Exponent, which describes the maximum length of an A-MPDU by the formula
2^(13+Exponent) - 1 bytes.
802.11ac allows values for the exponent ranging from 0 to 7, which allows the maximum A-MPDU length to range from 8 KB to 1 MB.
[MAX-A-MPDU-LEN-EXP7] ~ [MAX-A-MPDU-LEN-EXP1]