I've been using DD-WRT on my Archer C1900 v1 for some time now and it works very well. The current builds only work for v1 and not v2 and only for US and not CA hardware. The only issues I've found I posted about including channel widths for which the fix is to manually set the channels (rather than auto) and the regulatory domain. For the latter, I eventually just set the domain to US and enabled the 802.11d regulatory mode. That way my clients default to US when seen on the network.