Ubuntu – Why are two versions of software with identical names installed on Ubuntu 18.04, and can I remove one of them

GNOME Software does indeed tell you if something is a deb, snap or flatpak. If you click on an application and then scroll down past the screenshots you'll see the origin of the software was either from the Ubuntu archive, snapstore or flathub.

Is it just me who feels this hasn't been communicated clearly to the users or are the average users now expected to check developer blogs and launchpad for changes?

This was discussed online a lot over the last 5 months or so. Many news outlets covered it, including Phoronix and OMGUbuntu. We don't expect everyone to keep up with all the technical details of how Ubuntu is built. This is why we publish Release Notes which says

"Some utilities have been switched to the snap format for new installs (Calculator, Characters, Logs, and System Monitor). Snap apps provide better isolation which allows them to be upgraded to new stable releases during the LTS lifecycle. "

In addition, for many, the switch from deb to snap is largely irrelevant technical detail. It would be (for many) like the switch from Upstart to SystemD. A technical thing that matters to people who care, but the vast majority it doesn't matter.

I also commented on the further point of why things are delivered as snaps on the linked reddit thread, but am reproducing here in case the comment disappears.

When the LTS has just come out and most of the apps in the archive are at similar release numbers to those in the snap store, sure, it may be perplexing.

However, take into considering those people who are still running 14.04, a 4 year old release. When 14.04 came out everything in the archive was new and fresh. Cut forward 4 years and now a lot of that software is old. The same will be true for 18.04 users in the year 2022.

While it's true some people will upgrade to the next LTS, and many people did upgrade to 16.04. Not everyone does. We have a significant chunk of users who stick on older LTS releases. What we're doing with snaps is planting a seed for a tree that will grow in a year or so. Making sure that people who install the LTS can know they will get updates to software long into the future, and not be 'forced' to upgrade to the next LTS or interim release just to get the latest video player, utility or productivity application.

With 18.04, this was the first release where we pre-installed some snaps. This was partly to test the process, likely more apps will switch to being snaps in the future.

Now, all that said, snaps aren't perfect. Sometimes they can be slow to start, and the theming isn't right in all cases. We're working to fix these issues. I would strongly recommend if you have specific actionable feedback for the snap team, you take it to the forum where the developers hang out. https://forum.snapcraft.io/. The developers don't sit on Reddit all day (I do though ;) ) and need to hear these issues from users. We appreciate the feedback.