This is happening on an up-to-date (as of 2020 Apr/30) Eoan with
$ snap --version
snap    2.44.3
snapd   2.44.3
series  16
ubuntu  19.10
kernel  5.3.0-46-generic

>>> 15:55:37 andre@thinkpad ~ 
$ losetup -l
NAME        SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE                                        DIO LOG-SEC
/dev/loop1          0      0         1  1 /var/lib/snapd/snaps/core_8935.snap (deleted)      0     512
/dev/loop29         0      0         1  1 /var/lib/snapd/snaps/lxd_14729.snap (deleted)      0     512
/dev/loop19         0      0         1  1 /var/lib/snapd/snaps/gtk-common-themes_1506.snap   0     512
/dev/loop27         0      0         1  1 /var/lib/snapd/snaps/lxd_14709.snap (deleted)      0     512
/dev/loop8          0      0         1  1 /var/lib/snapd/snaps/core18_1705.snap              0     512
/dev/loop25         0      0         1  1 /var/lib/snapd/snaps/lxd_14663.snap (deleted)      0     512
/dev/loop15         0      0         1  1 /var/lib/snapd/snaps/lxd_14555.snap (deleted)      0     512
/dev/loop6          0      0         1  1 /var/lib/snapd/snaps/openstackclients_38.snap      0     512
/dev/loop33         0      0         1  1 /var/lib/snapd/snaps/gnome-3-34-1804_27.snap       0     512
/dev/loop23         0      0         1  1 /var/lib/snapd/snaps/lxd_14639.snap (deleted)      0     512
/dev/loop4          0      0         1  1 /var/lib/snapd/snaps/gnome-calculator_730.snap     0     512
/dev/loop31         0      0         1  1 /var/lib/snapd/snaps/juju_11454.snap               0     512
/dev/loop21         0      0         1  1 /var/lib/snapd/snaps/lxd_14583.snap (deleted)      0     512
/dev/loop11         0      0         1  1 /var/lib/snapd/snaps/charm_461.snap                0     512
/dev/loop0          0      0         1  1 /var/lib/snapd/snaps/lxd_14877.snap (deleted)      0     512
/dev/loop28         0      0         1  1 /var/lib/snapd/snaps/code_31.snap                  0     512
/dev/loop18         0      0         1  1 /var/lib/snapd/snaps/lxd_14594.snap (deleted)      0     512
/dev/loop9          0      0         1  1 /var/lib/snapd/snaps/lxd_14804.snap (deleted)      0     512
/dev/loop16         0      0         1  1 /var/lib/snapd/snaps/lxd_14680.snap (deleted)      0     512
/dev/loop7          0      0         1  1 /var/lib/snapd/snaps/gnome-characters_495.snap     0     512
/dev/loop34         0      0         1  1 /var/lib/snapd/snaps/lxd_14890.snap                0     512
/dev/loop24         0      0         1  1 /var/lib/snapd/snaps/lxd_14649.snap (deleted)      0     512
/dev/loop14         0      0         1  1 /var/lib/snapd/snaps/gnome-logs_93.snap            0     512
/dev/loop32         0      0         1  1 /var/lib/snapd/snaps/core_9066.snap                0     512
/dev/loop22         0      0         1  1 /var/lib/snapd/snaps/lxd_14611.snap (deleted)      0     512
/dev/loop30         0      0         1  1 /var/lib/snapd/snaps/lxd_14759.snap (deleted)      0     512
/dev/loop10         0      0         1  1 /var/lib/snapd/snaps/gnome-3-28-1804_116.snap      0     512
>>> 15:56:00 andre@thinkpad ~ 
$ snap list
Name               Version                     Rev    Tracking          Publisher   Notes
charm              2.7.4                       461    latest/stable     canonical✓  classic
code               ff915844                    31     latest/stable     vscode✓     classic
core               16-2.44.3                   9066   latest/stable     canonical✓  core
core18             20200311                    1705   latest/stable     canonical✓  base
gnome-3-28-1804    3.28.0-16-g27c9498.27c9498  116    latest/stable/…   canonical✓  -
gnome-3-34-1804    0+git.2c86692               27     latest/stable     canonical✓  -
gnome-calculator   3.36.0+git4.51b0dc05        730    latest/stable/…   canonical✓  -
gnome-characters   v3.32.1+git4.e06f0b2        495    latest/stable/…   canonical✓  -
gnome-logs         3.34.0                      93     latest/stable/…   canonical✓  -
gtk-common-themes  0.1-36-gc75f853             1506   latest/stable/…   canonical✓  -
juju               2.7.6                       11454  latest/stable     canonical✓  classic
lxd                4.0.1                       14890  latest/candidate  canonical✓  -
openstackclients   train                       38     latest/stable     james-page  classic

Also, all those volumes are appearing as mountable devices in Files app. And trying to delete them manually with losetup -d will not work.