Ubuntu offers two primary paths for the standard year.month products (ie. deb based systems).
Ubuntu LTS which are the first release on an even year, ie. 6.06, 8.04, 10.04, 12.04, 14.04, 16.04, 18.04, 20.04… Excluding the first LTS (which was a 2006-June release thus 6.06), all releases have been in April thus are shown as a .04 using the Ubuntu year.month format.
Ubuntu have releases every 6 months, so in between those releases are numerous (3 between each LTS) non-LTS releases, eg. between 20.04 and 22.04 there will be
- 20.10 or the 2020-October release
- 21.04 or the 2021-April release (an odd year so no LTS)
- 21.10 or the 2021-October release that has just hit UI (user-interface freeze)
All are treated as stable and secure, the primary difference is the length of time where security patches are provided for them (LTS releases are secure for longer)
For details about each release, the best place to go is the actual release notes, ie.
Note: I could have given other links for the Ubuntu release announcements, but my browser knows those links as I’m the person who posted them, and I know they contain full details and links.
Ubuntu LTS releases have two kernel stack choices
- GA or the kernel stack that the system is released with, or
- HWE or the hardware enablement stack; which upgrades for the first two years of it’s life, before settling on the GA stack of the next LTS.
Ubuntu 20.04 LTS was released with the 5.4 kernel, thus it’s the GA stack. Lubuntu 20.04 LTS media installed and defaulted to the GA stack, as did Lubuntu 20.04.1 LTS media.
At 20.04.2, if using the HWE stack, your system kernel upgraded to the 5.8 kernel, which was the kernel stack from 20.10 (which released months before 20.04.2). Lubuntu 20.04.2 & later media defaults to the HWE stack.
At 20.04.3, if using the HWE stack, your system kernel upgraded to the 5.11 kernel, which was the kernel stack from 21.04 (again 21.04 released months before 20.04.3)
At 20.04.4, if using the HWE stack, your system kernel will upgrade to the kernel found in Ubuntu 21.10 (currently impish and not released; 5.13 currently, but we’ve not reached kernel freeze yet so it may change; again 20.04.4 will be released a few months after 21.10 has been released.
At 20.04.5, if using the HWE stack, your system upgrades for the last time to the GA stack of the next LTS, ie. 22.04, again the release is a few months after 22.04 has been released.
Users of 20.04 with the GA stack upgrade through 20.04 to 20.04.5 too, but their kernel always remains on the stable 5.4 kernel; they don’t get access to later kernel modules (drivers) offered by later stacks.
FYI: If you want to see the release schedule for focal fossa you can see it here ; this is written purely from memory.
For details about the GA/HWE stack choices - I’ll refer you to the wiki. The stack you’re using can be changed post-install, and you can have both stacks installed (ie. I find useful for problem solving on occasion). You’ll also find some 3rd party software is only generated for the GA stack.
FYI: The LXQt that came with 20.04 used the LTS Qt5 stack (Qt 5.12.8), so LTS releases may not be the latest LXQt at release time, but will be the version that aligns with the latest LTS Qt5 stack available for security reasons.
Yes I’ve seen your requests for help with color but I have no answers there, so I’ve stuck to answering the generic Ubuntu questions [in this reply].