Described in Annex B of the Horizon Europe Work Programme General Annexes. A number of non-EU/non-Associated Countries that are not automatically eligible for funding have made specific provisions for making funding available for their participants in Horizon Europe projects.
For other eligibility criteria, see https://ec.europa.eu/info/funding-tenders/opportunities/portal/screen/support/faq/50252?topicIdentifier=HORIZON-CL5-2024-D3-02-08&topicIdentifierId=HORIZON-CL5-2024-D3-02-08&isQA=true.