Forbes is reporting[0] that they are using BitGo. FYI Salvadorians are not required to use chivo at all. The interoperability is the exciting part not chivo.
BitGo being another centralized custodial wallet antithetical to the white paper? I mean, my dollars are interoperable with every bank in America and that really doesn't excite me. They're also interoperable with the banks in El Salvador since both use the USD.
[0] https://www.forbes.com/sites/jonathanponciano/2021/09/07/el-...