I've got 21.02 on an Netgear R6260, and it's working pretty well. However, whenever I go to enable non-default VLAN tagging and management, I can no longer access the router (web ui or ssh) from the machine I was using to manage it, and I have to "factory reset" clear the settings. I did once find a forum topic that mentioned something like this, but it implied it was a solved problem or not applicable to this router (which uses DSA).
Is there some way I can fix this? I am right now using this router in production, because the 2.4 isn't working well on my R8000 since a new neighbor and their wifi moved in but if I can get this wndr3400 working nicely enough I can probably swap it out to assist with dev and testing. I did connect to the internal UART before flashing since it seemed like I might need that log to get it running (with the bad block partition stuff) but I didn't end up having to modify the stock firmware at all. (I'm a Linux dev by trade, and did actually even build a custom image for the device before I discovered one wasn't needed)
The catch (as with swconfig, BTW) is you need to define your br-lan.1 device explicitly (assuming you'll assign default VLAN 1 to your LAN bridge) once you start using VLANs. See my DSA VLAN script e.g.:
Hey, this is excellent, it did indeed fix it! Afterward I had to go in to the existing br-lan "Device" and adjust the vlan/primary vlan ID assignment there as the script indicated (I wanted to make one network port on my secondary vlan), then I did the rest of the setup of creating an interface pointed at the new br-lan.10 device. I can access the device still through both lans.
I had not played much with the swconfig vlan stuff, but just knew that adjusting vlan settings in LuCI didn't break my access, unlike with DSA. Would it make sense to add some kind of "VLAN Wizard" to LuCI? Or some other method to "enlarge the pit of success" to make it easier to get right than wrong? I don't have experience in that codebase, but I do know Lua. (FWIW I did actually go with 21.02 on this device for now, but I have tested the 22 RC's on another device and am fine building images myself, etc.)
It might, or maybe just a warning that you need to set the VLAN and modified interface name explicitly when fiddling with VLANs might do. OpenWrt is phasing out Lua for the web interface, AFAIK most (or all) of it is client side nowadays. @jow can probably fill you in on that.