Guidance on this is contained at https://www.gov.uk/guidance/eu-domain-names-what-you-need-to-do-before-the-end-of-the-transition-period, and this will apply to all UK organisations. You should follow the advice here, including to contact your domain registrar to understand what this means for you. You should also contact your Lead Partner or Joint Secretariat contact to seek their advice.
A number of UK-based ETC project partners have already transferred domain registrations to one of their EU project partners, and this may be something that you wish to explore within your project.