Web & Android are base on restAPI, no local store
Cells-sync do the synchronization between cells & local store so grpc is used for synchronization.
Cells-sync has no interface to bypass the certificate (like you have in browser). You need to install the self-sign cert rootCA.pem to system trust root. Once the rootCA.pem is added to the system trust, your cells-sync can ‘trust’ this self-signed cert