Error in Common Ubiquiti Procedures for XM AirMax devices?

[Joe Ayers]

Openwrt Github commit notes, Forum posts, and Documentation, refer to:

"The mtd partitions layout for XM-type devices changed from AirOS v5.5
to AirOS v5.6. Before installing OpenWrt, downgrade first to AirOS
5.5."

reference:  https://openwrt.org/toh/ubiquiti/common

While the documentation is a path to succeed loading openwrt firmware,
this commit fixed the soft-brick issue (soft-brick meaning tftp
recovery with serial cable is possible):
https://github.com/openwrt/openwrt/commit/076d58d3440f382c536ea8874f58b0df23c263bc

It is a key message, that openwrt firmware after this commit, will no
longer soft-brick the device, not communicated.

The key misunderstanding is around the root cause due to Ubiquiti
tightening up uboot to further check partition sizes.   The root cause
was identified as a bad openwrt size definition that older versions of
uboot accepted, without end user awareness.

The reason I raise this issue is due to users in the
https//www.arednmesh.org community struggling to downgrade to AirOX
v5.5, and we spend time working with them only to do tftp
"hold-reset-button" firmware loads to succeed as quickest path.

Note, however, there are still issues where newer Uboot versions
expect images to have particular naming conventions, which are also
addressed in later fixes:

https://github.com/openwrt/openwrt/commit/6009b3fd586a1fd91400074080afb9545c6cf7e2

Thus, firmware before this time will not tftp "hold-reset-button" load
due to this 2nd issue, but not soft-brick the device.

I've not found the time to track down how to contact the relevant
stakeholders to address this issue in the documentation, consequently,
blasting out in this list in hopes of triggering someone to update the
relevant openwrt documentation to add more clarity to the issue.

Regards,
Joe AE6XE