I have just upgraded to MAC OS Big Sur and all of my 'smart vpn' ssl connection will not connect to a draytek 3900. Works fine on PC client.

To get around this i have tried setting up ikev2 connections, these are also not working.

I have found this snippet from other users with the same problem
We have upgraded the proposed ciphers in L2TP IPsec VPN to also propose SHA-256 for the Child SA in IPsec. The issue seems to be that the server is accepting SHA-256 cipher for the child but maybe dropping the ESP encrypted packets with SHA-256 HMAC. This maybe because the server is assuming a SHA-256 HMAC with 96 bits instead of the standard 128 bits. Switching the SHA-256 HMAC output from 96 to 128 bits should fix this issue."

is there anything I can do to get around this problem on a draytek 3900?

many thanks