@Tranas Check that your public IP address is what you're using to access your SSH server from outside your network: https://www.whatismyip.com Ping <yourname.dyndns> domain and compare the IP address...

What's your AC wi-fi adapter model ? Normally the associated/lnk speed for 2.4GHz band should be nearly 300mbps for A6. Have you tried to check for high congestion on the 2.4GHz band in your area -...

@oldster You should have something like this on the bottom of your device :

On the bottom of the device should be a sticker with the model, HW version and credentials. Actually there are pretty obvious differences on the box picture itself as well.

Wasn't it more like an AP (also nano routers in the past) feature ?

Have you tried to set Channel width to 40Mhz (for 2.4GHz band) and turn on MU-MIMO ?