I’ll provide my 2c, which may contain something useful.
I usually opt for a normal release-upgrade after reading the release notes and ensuring no issues where discovered in QA that relate to packages I was using, or hardware I have, then ensuring my backups are updated & if I destroyed my system I’d be able to re-create it somewhat easily.
On many of my systems, I often lack disk space, thus can’t achieve the release-upgrade without lots of deletions, so I’m often implementing my ‘backup’ strategy anyway…
Should I have problems with the release-upgrade OR just lacked disk space, or even lacked time (as re-install is so fast!) I just non-destructively re-install the release I want to move to, as this will fix package issues and gets to the end result so quickly, further doesn’t need to disk space that is required by a release-upgrade.
I talk about it here, where you’ll find a link to another description found on Lubuntu’s discourse (it was used as a testcase for Lubuntu from 19.04 thru 24.04 though is no longer used)
In the link I provided, I didn’t cover 3rd party packages, as experiences there will depend on how the 3rd party packager worked, did they consider the release-upgrade process (if so it’ll work) OR they ignored it (you can experience problems), so assessing this is more complex & rather specific to what & from where (ie. third party source). I personally use little third party, and just assume I may need to fix those myself afterwards.
That method isn’t an option if using Ubuntu 24.04 LTS Desktop as it forces format of the / partition due to a bug discovered in QA where forcing format is the current fix, but you mention Lubuntu which is one of the flavors using the calamares installer thus it is an option.
A release-upgrade from 20.04 will only get you to 22.04, after which you can re-assess the situation for the next jump which will get to you 24.04.
The best place for details on issues is of course the release notes, so have you looked? That will of course include Ubuntu’s and Lubuntu’s (we only provided an announcement for 22.04.5 but did provide 22.04.4 release notes but Ubuntu’s release notes are most critical for release-upgrades), then you can look at the upgrade instructions, but do note the release notes contain the most useful detail on issues.
The point release status is also useful; esp. in the earlier days (as 22.04.1 dealt with release-upgrade issues), as well as point release changes (Jammy Jellyfish Point-Release Changes) but we’re so far from 20.04->22.04 that you’ll probably only gain detail when you get to the 22.04->24.04 upgrade.