This web part finds all the Office 365 or AAD Security groups a user is a member of or all the members present in such a group. It can be used as an admin utility to quickly check the membership of any user or group from within a SharePoint page itself. The retrieved results can also be exported to a CSV file.
Open this sample in the gallery (popup panel): Open in gallery
Source: https://github.com/pnp/sp-dev-fx-webparts/tree/main/samples/react-check-user-group