Hello,
When I try to install OpenWrt from newest stock 5.0.3 (EAP245(EU)_V3_5.0.3_20210604) then after choosing file location and pressing Update button, system shows info: bad file
Please follow the install instructions as listed in the commit message. It's impossible to install OpenWrt using only the web GUI, but it really isn't that hard:
ssh into target device and run cliclientd stopcs
upload factory image via web interface
They are replying via email, so this is just the typical header to a quoted message.
TP-Link adds a cryptographic signature to their firmware, and OpenWrt doesn't have the key required to generate these. Normally, the firmware will find that the OpenWrt factory image is not "trusted", and will refuse installing it. By issuing the cliclientd stopcs command, we're telling the firmware that it can trust any image we provide, which allows us to install OpenWrt.
Depending if you installed the 21.2.0 or the master snapshot (which the device page still links to?), you only have luci on 21.2.0, for the snapshot you need to first download luci with the use of ssh.
But then you need to connect the access point directly to a computer since it works like a dhcp server/router after the install (which is kind of super awkward and very strange basic setup for a PoE access point!) so you need to find the old PoE converter and plug it to the computer. Then your computer will get a IP address from the AP and you log in to 192.168.1.1. Then you change the LAN IP setup from Static address to DHCP client. (Note that this will loose connection to the router and you need to force the setup) Then you can connect it as an actual access point to the switch or router and log in to it as you usually do through the router when you have an access point.
Longer than that I haven’t got yet. But since we are already here we can take the next question right away. The eap245 gets delivered in OWRT with both swconf and DSA switch setup possibilities, which one are we supposed to use and are both working?
This target doesn't use DSA at the moment, and is still on swconfig. I think they're currently looking at using the upstream qca8k driver on the ath79, which would use DSA. But that's only relevant for master (i.e. snapshot builds), 21.02.x will stay on swconfig.