@erict: indeed the authentication key name check is too strict at the moment since it only allows word characters (0-9, a-z, A-Z and underscore). I just committed a fix which will also allow the minus character (https://github.com/veyon/veyon/commit/768feeb53c11d7a1f5e5fa4d8378d795c73cc1ad). It will be part of Veyon 4.5.7 next month. In case you build packages on your own, you can simply do this for the latest 4.5 branch.
Besides that, importing keys via veyon-cli should work with the following command:
veyon-cli authkeys import veyon_master/public public-key.pem