As a temporary solution you might want to proxy requests to directadmin via nginx/apache, and set ssl ciphers there.
I have no idea how I can do that.
It will be ok for now, but I actually hope that Directadmin staff will give us the possibility to use or own safe ciphers.
There are multiple other threads about that here.
https://forum.directadmin.com/showthread.php?t=52026
https://forum.directadmin.com/showthread.php?t=51854
https://forum.directadmin.com/showthread.php?t=51245
This is security, And I hope they take that serious!