The Government should offer EU musicians a free 90 day working visa for the UK without requiring them to hold a certificate of sponsorship from an approved promoter. This should then be used as leverage with the EU to negotiate the same for UK musicians and crews to work in the EU.
You may be interested in these active petitions
There are press reports that the Government did not offer this during Brexit negotiations and that is why the EU could not offer visa free work for UK musicians. They understandably need it to be a reciprocal arrangement.