On our mesh we have Ubiuity bullets, Ubiquity Nanostation M2, and Ubiquity Nanobridge M5.

We are able to change channel width on the M5 from 20mhz to 10mhz or even 5mhz.

These options show as available on the bullet or Nanostation, but the device will not save the configuration away from 20mhz and reports that it is not available.

We are using V3.1 on all devices.

Thanks for your feedback

This is expected behavior. With M3 or M5 units, changes are permitted because there is no legacy compatibility to maintain. With the M2 line, Ubiquiti hardware can do things that Linksys hardware can't do. For example, wider or more narrow channel widths are not supported by Linksys. The closed driver support for the Broadcom chipset probably does some additional tricks. The problem is that without documentation like the Atheros chipsets offer, how to do these tasks is not easy to find out.

We have provided a method to side step this problem. If you change the default SSID (and create a separate, non-compatible network in the process) the software in M2 devices can save a different channel bandwidth.

This is one feature inserted to protect "one network, works everywhere" compatibility in the 2Ghz band. We realize that most users will continue to use default values in this band and the restriction makes sense. If you have specific reasons to create a separate network, you may do so by changing the SSID. As you do so, the other changes can be saved as well.