The mobility of UK-bound EU performers will not immediately be impacted by Brexit.
In the recent weeks, the UK Home Office has offered assurances that under a unilateral decision (not reliant on a deal) the mobility rules governing UK-bound EU performing artists will remain essentially “as is” until (at least) December 31, 2020.
This rule has now been written into Appendix EU which is contained in the immigration rules: https://www.gov.uk/guidance/immigration-rules/immigration-rules-appendix-eu. To find the relevant passage, click on “Annex 1 – Definitions” and scroll down to “specified date” and look at part (b) “if the United Kingdom withdraws from the European Union without a Withdrawal Agreement;” the date and time have now been put into the Appendix as 2300 GMT on 31 December 2020. It’s a bit of a jumble to unpick but it appears that this is the specific subparagraph that is the basis for what the Home Offices assurance: “- sub-paragraph (a) of the entry for ‘relevant EEA citizen’ in this table”
So that’s a bit of good-ish news.