Firstly, I would like to say that DD-WRT will not work on an Archer C7 Version 1.x, if the 5GHz card is still connected. This is the result of my work.
I did the following:
I took out the QCA9880-AR1A 5GHz card. The TP-Link firmware was still on the unit. However, the web-interface would not work without the 5GHz card. So I had to put it back in.
From the 'tplink_archer-c7-v1' directory, I downloaded the 20160404 beta. Due to the small flash (just 8 mb), there are two files: factory-to-ddwrt.bin and the tplink_archer-C7.bin.
With the 5GHz card in, the factory-to-ddwrt.bin install went quite well. After the install, I switched off the unit and took out the card. The unit booted up just fine without the card. I did the final update to tplink-archer-C7.bin. That went fine as well, as I rebooted and had a good look around. No problem.
The only little odd thing I noticed was that DD-WRT had the version of the unit 'Version 2' instead of 'Version 1.1' which it is.
Then I switched off the unit, put the 5GHz card back in and the unit was in a 'bricked' mode. No response from the unit. I was able to verify this with the tcpdump I had going on eth0 on my computer.
Thus, if you want to use DD-WRT on an Archer C7 Version 1.x, you will need to take the 5GHz out. If you want to have 5GHz wireless, you will need to replace the card.
OpenWRT/Lede will both work with the card still in, but neither will be able to recognise the card (same problem with the lack of open source drivers).
Sadly, for very complicated reasons (which I don't totally understand), there will never be any open source drivers for the QCA9880-AR1A chip.
I will write this info on the wiki page as well. If anyone else could confirm this or had another experience, please let me know.
It would have been reasonable if that information could have been on the DD-WRT wiki. But that's not possible since it is not easy obtaining a DD-WRT wiki login.
Thus, I will put some information on a webpage with the warning not to install DD-WRT on an Archer C7 Version 1.x with the unsupported 5GHz card still attached.
Otherwise, without the 5GHz card, DD-WRT works just fine on the Archer C7 Version 1.x
It would have been reasonable if that information could have been on the DD-WRT wiki. But that's not possible since it is not easy obtaining a DD-WRT wiki login.
Thus, I will put some information on a webpage with the warning not to install DD-WRT on an Archer C7 Version 1.x with the unsupported 5GHz card still attached.
Otherwise, without the 5GHz card, DD-WRT works just fine on the Archer C7 Version 1.x
It would be more convenient to have it on the DD_WRT wiki.
However, a Google search using Archer C7 v1 site:dd-wrt.com brings up that information as well.
If this could be on the DD-WRT wiki, that would be even better.
I am of the opinion that the DD-WRT version for the Archer C7 Version 1.x should not be released, since the router will not boot up after installing the DD-WRT firmware (unless the 5GHz card is taken out).