To answer your questions:

Why are they duplicated?

⇢ They're different revisions (versions), not duplications.

Can I remove the older package to ensure better disk space management?

⇢ Yes. It's your computer, after all.

How do I remove the older package?

You can do this in Terminal like this:

snap remove {snap} --revision={revision}

You can also tell the system how many past versions to limit itself to like this:

sudo snap set system refresh.retain=2

^{Note: The value must be between 2 and 20, and a number like 2 or 3 is generally recommended to save storage space and allow a rollback in the event of a bad update.}

If you would like to list all the snaps and their versions, you can run this command:

snap list --all

Which will give you something like:

Name                 Version                     Rev    Tracking         Publisher   Notes

bare                 1.0                         5      latest/stable    canonical✓  base

canonical-livepatch  10.0.1                      119    latest/stable    canonical✓  disabled

canonical-livepatch  10.1.2                      126    latest/stable    canonical✓  -

core                 16-2.52                     11798  latest/stable    canonical✓  core,disabled

core                 16-2.52.1                   11993  latest/stable    canonical✓  core

core18               20211028                    2253   latest/stable    canonical✓  base

core18               20211015                    2246   latest/stable    canonical✓  base,disabled

core20               20211115                    1242   latest/stable    canonical✓  base,disabled

core20               20211129                    1270   latest/stable    canonical✓  base

gnome-3-28-1804      3.28.0-19-g98f9e67.98f9e67  145    latest/stable    canonical✓  disabled

gnome-3-28-1804      3.28.0-19-g98f9e67.98f9e67  161    latest/stable    canonical✓  -

gnome-3-34-1804      0+git.3556cb3               77     latest/stable/…  canonical✓  -

gnome-3-34-1804      0+git.3556cb3               72     latest/stable/…  canonical✓  disabled

gnome-3-38-2004      0+git.cd626d1               87     latest/stable    canonical✓  -

gnome-3-38-2004      0+git.6ba6040               76     latest/stable    canonical✓  disabled

gtk-common-themes    0.1-52-gb92ac40             1515   latest/stable/…  canonical✓  disabled

gtk-common-themes    0.1-59-g7bca6ae             1519   latest/stable/…  canonical✓  -

snap-store           3.38.0-66-gbd5b8f7          558    latest/stable/…  canonical✓  -

snap-store           3.38.0-64-g23c4c77          547    latest/stable/…  canonical✓  disabled

snapd                2.53.2                      14066  latest/stable    canonical✓  snapd,disabled

snapd                2.53.4                      14295  latest/stable    canonical✓  snapd

Need a Script?

IMPORTANT: You will want to check the output of snap list --all on your computer before continuing, and the following is a script that should not be copy/pasted without sanity checking if you are using a locale that is not en_US.UTF-8.

The Script:

#!/bin/bash

# This script will remove disabled snap revisions.

set -eu



LANG=C snap list --all | awk '/disabled/{print $1, $3}' |

    while read name rev; do

        snap remove "$name" --revision="$rev"

    done

This will run snap list -all and extract the lines that contain the word disabled. This will be different depending on your locale, so check the output of the function first, then update awk '/disabled/ to replace disabled with the label that is found in your output.

Save the script to a file (for example scrub-snaps.sh) and then set it as being executable:

sudo chmod +x scrub-snaps.sh

Now you can run it, remembering to use sudo:

sudo ./scrub-snaps.sh

^{Note: sudo was not part of the script, but can be added if you prefer to have it in there. Either way, you'll be prompted for a password if required.}