Does Ubuntu keep a list of version upgrades?

A list or command? No.

But there will be clues that a detective can use to put the pieces together.

1. /var/log/installer includes files that will tell you what version was originally installed and when.

   There are different installers and different versions out there, so browse the contents of that directory until you find a useful file!

   Here's an example. See if you can figure out which release was originally installed:

   $ less /var/log/installer/casper.log 
   [...snip...]
   Source list entries for this disc are:
   deb cdrom:[Ubuntu 22.04 LTS _Jammy Jellyfish_ - Release amd64 (20220419)]/ jammy main restricted
   

   That was easy!

2. dpkg -l | grep linux-image will list all the previous (and current) kernels installed by dpkg. Kernels are specific to a single release of Ubuntu, and metapackages like HWE are clearly labelled.

   Here's an example. See if you can figure out which release this system was upgraded to:

   $ dpkg -l | grep linux-image
   rc  linux-image-5.15.0-25-generic              5.15.0-25.25                             amd64        Signed kernel image generic
   rc  linux-image-5.15.0-48-generic              5.15.0-48.54                             amd64        Signed kernel image generic
   rc  linux-image-5.15.0-52-generic              5.15.0-52.58                             amd64        Signed kernel image generic
   rc  linux-image-5.19.0-21-generic              5.19.0-21.21                             amd64        Signed kernel image generic
   rc  linux-image-5.19.0-23-generic              5.19.0-23.24                             amd64        Signed kernel image generic
   rc  linux-image-5.19.0-35-generic              5.19.0-35.36                             amd64        Signed kernel image generic
   ii  linux-image-5.19.0-38-generic              5.19.0-38.39                             amd64        Signed kernel image generic
   ii  linux-image-5.19.0-40-generic              5.19.0-40.41                             amd64        Signed kernel image generic
   ii  linux-image-generic 
   

   Look at the kernel versions: The jump from 5.15 to 5.19 is important. It means EITHER that the system was release-upgraded from 22.04 to 22.10 OR that it's a 22.04 system using an HWE kernel.

   Next, look at the metapackages: linux-image-generic only. No HWE metapackage. That rules out one possibility.

   So we can deduce that this example system installed 22.04, and later release-upgraded to 22.10.

   That was also pretty easy after you know what to look for.