Edit with corrections thanks to bill888
That's not exactly correct - I've been experimenting with one of my HH5As and these are the results between 2 OpenWRT routers as I only have a 100mbit contract:
Invalid results
root@OpenWrt:~# grep name /etc/board.json
"name": "BT Home Hub 5A"
"name": "wifi",
"name": "dsl",
"name": "dimmed",
root@OpenWrt:~# iperf3 -c 192.168.1.1
Connecting to host 192.168.1.1, port 5201
[ 5] local 192.168.1.152 port 42600 connected to 192.168.1.1 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 23.7 MBytes 198 Mbits/sec 0 354 KBytes
[ 5] 1.00-2.02 sec 24.1 MBytes 198 Mbits/sec 0 445 KBytes
[ 5] 2.02-3.02 sec 24.9 MBytes 210 Mbits/sec 0 475 KBytes
[ 5] 3.02-4.03 sec 24.5 MBytes 204 Mbits/sec 0 498 KBytes
[ 5] 4.03-5.01 sec 24.4 MBytes 208 Mbits/sec 0 498 KBytes
[ 5] 5.01-6.02 sec 25.5 MBytes 211 Mbits/sec 0 498 KBytes
[ 5] 6.02-7.01 sec 24.4 MBytes 206 Mbits/sec 0 522 KBytes
[ 5] 7.01-8.04 sec 24.8 MBytes 202 Mbits/sec 0 522 KBytes
[ 5] 8.04-9.04 sec 24.8 MBytes 209 Mbits/sec 0 522 KBytes
[ 5] 9.04-10.00 sec 25.5 MBytes 222 Mbits/sec 0 522 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 246 MBytes 207 Mbits/sec 0 sender
[ 5] 0.00-10.00 sec 246 MBytes 206 Mbits/sec receiver
The host on 192.168.1.1 that is facing the internet is a Linksys EA7500v1 (21.02.0) and the client HH5A is a snapshot build. I've enabled Software flow offloading and have added a custom script that I got from this post