Ubuntu 21.04: how to enable Wayland?

Hello I have upgraded to Hippo (Ubuntu 21.04), but my session is still using X11. At the login screen, the only choice I have are «Unity» or «Ubuntu». I guess this is probably because my current install is really old, but upgraded every 6 months. On my others computer, Hippo is running under Wayland by default. But is there a way to force Hippo to use Wayland, or at least to have it available as an option at the login screen ?
Thanks a lot.