"Of course many enthusiasts of Brexit have no interest in the culture of other countries"

That's an easy stereotype and it may be true of some, but certainly not of others. I would expect anyone sufficiently interested in music to come onto this site to have at least some interest, even if they do support Brexit.

I can immediately think of two folk bands, Blowzabella and Topette, who play regularly on both sides of the Channel and who are made up of both British and French musicians, and presumably will face difficulties whether they are performing in the UK or in Europe. The last time I spoke to a member of Blowzabella they still had no clear idea how it was going to work out - admittedly that was a few months ago but I have seen nothing since then to suggest that special arrangements to ease these difficulties are close to being put in place.