Have you ever been able to solve this? Reading through all the issues people are having ( e.g. https://forum.seafile.com/t/cant-connect-mac-client-network-error-handshake-failed/21882, https://forum.seafile.com/t/tls-v1-3-support-of-clients/6054/16) and the developers’ responses there I get the impression Macs haven’t been supported anymore more quite some time.