Apologies upfront I haven't been keeping up to date with the alpha, but I haven't seen mention of a PA Launcher for Linux yet within the forum topics and was wondering if one has been made available yet.
So no then. The last set of patch notes with details of this is 50742, after this the patch notes are silent on the matter.
There is Steam at least (if you convert to Steam, later on you can still use it with their direct launcher).
Activate your key from a VM running an un-activated install of Windows and then delete the VM. All recent versions of Windows will run for a while without activation. Its not like most Linux people don't keep a Windows box or VM around for oddball tasks like this anyway.