X11 not found

Today I noticed that I only have wayland not both of them
how to install X11 alongside wayland and switch them If I want?

yay -S plasma-x11-session

Assuming you are on KDE.

What if i’ve already upgraded to plasma 6.4 and rebooted?!

If you’re only using Wayland, you’re good to go. If you want x11, install plasma-x11-session and reboot.

Yes, i just want to have X11 as an alternative option cause my pc is very old.