WhatsApp, Signal, & some others use the same open standardization end-to-end encryption. It’s the bare minimum bar for acceptable (but most of these apps require a primary Android/iOS device to hold the key which plays right into that duopoly as well as making smart phones a requirement rather than optional).
Discord has no e2ee, many rooms require phone numbers, the service is proprietary, they have trackers, they send cease & desists to projects wanting to be alternate clients. These are not the hallmarks for privacy or security.