Saxo is an online trading and investment platform for private and professional clients, offered through web and app channels. It is run by Saxo Bank A/S, a Danish bank headquartered in Hellerup, and client agreements are made with the Saxo entity in the client's country of residence. It is a hosted service rather than software clients install, and it is not open source.
As a Danish company, Saxo Bank A/S is an EU controller subject to the GDPR. Saxo's website states that the group is part of J. Safra Sarasin, which has acquired a majority stake, so the ultimate owner is a Swiss group under non-EU jurisdiction. The privacy notice allows transfers to countries outside the EU and EEA under binding corporate rules and standard contractual clauses, but does not state where data is stored. A European organisation should weigh the non-EU parent and these transfers, and request the hosting location in writing.