It will be usable with Mir as SDL has added support for Mir.

With Mir and SDL playing nice together, games using it will run natively under Unity 8 on Mir – no fuss, no hassle, and no discernible difference from that of the traditional X server.

Mir is the display server used in last ubuntu versions developped by cannonical

Reference: Some of Linux’s Most Popular Games Will Run Natively On Mir