Since 1 January 2021, UK nationals are no longer citizens of the EU and are therefore subject to the same rules that apply to third-country nationals, including quotas.
If you are a UK national and already had residence rights in Switzerland before 2021, you benefit from special provisions under the agreement between Switzerland and the UK on acquired rights.
Based on an agreement between Switzerland and the UK, persons from the UK supplying cross-border services in Switzerland for up to 90 working days per calendar year (short-term work) can do so without any work permit but using the online notification procedure. This applies to workers posted by a company based in the UK regardless of their nationality, and to self-employed service providers based in the UK with UK nationality.
Admissions of cross-border service providers from the UK for more than 90 days per calendar year, are subject to work permits. Applications must be submitted by the employer to the competent cantonal migration or labour market authority.
You can find further information on the web page of the State Secretariat for Migration (SEM).