The default wg setup still uses private/public keys, although the psk does add an additional layer. I don't know if this will work or not, but you may be able to manually add them to each node by using the wg command. I don't know if the config will stick permanently though. I'll be trying this myself after I finish setting everything else up. Do this by "wg genpsk > somefilename" then "wg set peer preshared-key "