Not a lot to report I'm afraid.

I've changed my configuration slightly - although the wireless link to the garage was working fine, I have installed a backup server in there and decided to dig a bit of garden in order to run an ethernet cable out to the garage. So I now have the 2927ax as root and 3 AP906s as wired nodes. I don't have any noticeable problems with devices connecting or roaming, all working fine as far as I can tell. Interesting that you had a problem with the 903, they worked fine in mesh mode with my previous 2926ac. My Channels are 11 on 2.4 and 36 on 5. I have 4 SSIDs on 2.4, one being dedicated to a group of Blink devices, and 3 on 5GHz matching the other 3 on 2.4. I haven't bothered turning band steering on but may experiment....

The 906 is not compatible with ac routers in mesh as far as I know. I previously had 960c's which were compatible.

I've recently upgraded from an AP-902 to an AP-906, with a wired connection to a non-wifi 2862.
The AP-902 has been running fine for seven years, and for the whole of that time my HP LaserJet 400 M401dw printer has never given any trouble when connected to the AP-902 on 2.4GHz wifi. (The M401 does not support 5GHz wifi).

However, on the AP-906, having set up the same 2.4GHz SSID and PSK, the printer refuses to connect to the AP-906, but instantly connects OK to the AP-902 when it is re-installed. (I'm running only one access point on the 2862).
Nothing I've tried so far has resolved this problem.
Searching the internet reveals that others have reported similar problems with this printer but on different brands of access point - and in some cases these problems were resolved when a new router firmware was installed.

I'd be interested to hear from others on this forum who might have had a similar problem, especially if there's an explanation of what may be causing the problem. My AP-906 is running the latest v1.4.9 firmware.

After many hours of troubleshooting the WiFi connectivity problem on my HP M401dw LaserJet printer it appears that, despite HP's claims in its documentation and on a printout of the printer's configuration page, this, and a number of other not-so-old HP printers do NOT in fact support WPA2 or WPA3.
The only way to get my printer working again was to create an SSID on the AP-906 that uses the inherently insecure WPA / TKIP.
I'm going to have to find a VLAN solution to isolate the printer on my network if WPA is going to be the only option.
... so it was clearly not a problem with the AP-906

Trawling the web, there are many others complaining about HP's misleading claims that printers only a few years old support WPA2 when they clearly do not.

At one point in the troubleshooting process my printer was giving '79 Service Error' messages on its display, then repeatedly rebooting, thus preventing access to the configuration menus. This message 'feels' like a hardware problem, but it was eventually solved by deleting the AP-906s SSID that was configured with WPA2 / WPA3, in favour of one using only WPA.

Hope this is of help to any others users of HP printers experiencing similar problems.

Posted in error

What's the state of Draytek's WiFi APs and using a Router like a 2865 as a Mesh root these days? Any improvements? Does is now work flawlessly as advertised?

I don't know about "flawlessly" but my mesh consisting of a 2927ax root and 3x AP906 nodes appears to work OK - although "upgrading" the 2927 to 4.4.5 tended to screw things up. Fine on 4.4.3.1. Caveat is that my 3 AP's are wired - and I've yet to be convinced that "mesh" mode offers any great advantages in this scenario.