The register
The register lists GlobalGiving UK in London as a licensed sponsor on Skilled Worker, an entry that goes back to at least 2026. Rating on the current register: Worker (A rating).
Companies House lists it as Globalgiving UK, number 05824642, incorporated 2006: 20 years of filings behind the name. Registered office: Office 605 Albert House 256-260 Old Street, London, EC1V 9DD, EC1V 9DD. Its filed activity puts it in it, software and media.
A licence says an organisation may sponsor; it does not say it is hiring today. The way to find out is the same as for any employer: the careers page, the job boards, and a direct approach with a UK-style CV that says early that sponsorship would be needed.