Multipass is just for shell, but you can install the ubuntu desktop and install an rdp tool.
Based on this ubuntu tutorial here is how you can do that:
First go into the shell of your multipass instance, multipass shell my-multipass-name. Replace 'my-multipass-name' with your multipass instance name. If you don't know the name, use multipass list to find all instances.
Run sudo apt update && sudo apt upgrade to update your multipass system.
After that's done, you need to install the ubuntu desktop and an rdp tool, sudo apt install ubuntu-desktop xrdp. APT should get you all the packages necessary.
Once you get the neccesary packages, you need to set a passwd for remoting into the system. sudo passwd [username]. Replace [username] with the username of your machine. If you didn't create a new user, the default is ubuntu.
Your guest ubuntu is now ready! Now we have to use your host system.
Install a program that uses xrdp:
Windows: You have the 'Remote Desktop Application'. Enter the IP (can be found in multipass list.
macOS/iOS: Install the 'Microsoft Remote Desktop' in the app store.
Linux: Remmina, you have to also have remmina-plugin-rdp along with the default remmina package on your host, otherwise it won't work.
