To install VirtualBox on Ubuntu 26.04, follow these steps.
Step 1 : Update.

Step 2 : Install VirtualBox. The package is in multiverse.


Step 3 : Check the version.

Step 4 : Download the Alpine virt ISO (change the URL if Alpine has a newer release).

Step 5 : Create the VM. --basefolder avoids a path with spaces.

Step 6 : Start the guest window from the CLI. The terminal returns to the prompt.

You have installed VirtualBox on Ubuntu 26.04.