composer prompt settlement process is killed - Increase Swap space

First, see if there is set swap on Ubuntu:

sudo swapon --show

If nothing in the display, indicating that there is no set swap.

Create a swap file, and activate:

sudo fallocate -l 1G /swapfile
sudo chmod 600 /swapfile
sudo swapon /swapfile

View, swapon there content.

See more swap settings here https://linuxize.com/post/how-to-add-swap-space-on-ubuntu-18-04/