You can read more detail here: https://r1.dotdigital-pages.com/p/49LX-12T5/all-gp-practices-using-emis-web-optum-or-systmon-e-tpp-are-legally-required-to-activate-access-to-pseudonymised-gp-rec-ords-using-the-open-safely-research-platform-by-september-2025
NHS England has also provided some further detail for reference here: https://transform.england.nhs.uk/information-governance/frequently-asked-questions/#questions-about-opensafely