clean install: you make a backup, nuke the computer, install a fresh upgraded copy of the distro you want from a live usb, copy your data again to the computer.
upgrade: you wait ‘till the distro’ developers release an upgrade you can directly install from your soon to be old distro, you use a command like sudo do-release-upgrade
and why do you upgrade like that?
Upgrade if it’s not too far behind. Last upgrade there was an issue with one package related to Waydroid which I updated via manual install to fix and they fixed it about two weeks later in the package manager so it doesn’t happen anymore anyway.