Current releases of Ubuntu, beginning when I am not exactly sure, no longer require a separate swap partition. A swap file can be used instead. This is definitely the case for Ubuntu 18.04 and Ubuntu 20.04.
In Ubuntu 20.04.1 if the OS installer is not directed to use a swap partition a swap file will be created in root.
The default size of the swap file is 2GB.
This many not be sufficient for the amount of RAM installed to a contemporary system.
Especially if system is a notebook where hibernation is required. This needs a much larger swap file/partition.
Helpful information about swap files and swap partitions for Ubuntu (and likely other Linux OSes) can be found in these links:
https://help.ubuntu.com/community/SwapFaq
https://bogdancornianu.com/change-swap-size-in-ubuntu/
The second link refers to what Ubuntu users will find after a default swap file is created.
Included in the first link is a method to remove a swap partition and create a swap file to replace it.