No idea. The last update was 2015, but a three year gap is a pretty normal release cadence for it:
http://www.6809.org.uk/evilwm/
I’ve never had a corrupted xauthority. I’d guess there’s a bug in some component other than X. (Does X11 even create the .Xauthority? Isn’t that the display manager (like xdm)’s job?)