SWAP

In 2020s, devices with 2GB of RAM have been a basic requirement for modern usage with UI, web browsing and video playback.

However some devices are produced as budgets phone with 1GB / 1.5GB, or even 256MB on those ancient devices.

With memory reserved by kernel for something like modem, there is even only 0.8GB /1.3GB available in userspace.

SWAP or SWAP file can be added for additional memory, which enables you to run Phosh or Plasma Mobile with smaller RAM, and even use Firefox to browse the web or playing video, etc.

Partition
To add some swap with unused partitions:

Swapfile
Or files:

fstab
And add swap partitions and files into.

OpenRC
Then make swap mounted by default.