.heic photo format, how to handle/export it?

I got a new cell that saves photos in.heic format, how to manage / export it? I tried with kolourpaint but nothing. Thank you.

Ubuntu 22.04 quick start

install heif-gdk-pixbuf for support in at least eog (Eye of GNOME, GNOME Image Viewer).
install heif-thumbnailer for file manager (nautilus, nemo) thumbnails.
The available versions of Geeqie, ImageMagick, gThumb and many more (see below) have built-in support.

Official packages

Starting with Ubuntu 20.04: At least for eog (Eye of GNOME, GNOME Image Viewer), you have to install the package heif-gdk-pixbuf (no PPA needed). In a terminal run:

sudo apt install heif-gdk-pixbuf

This will install libheif1 and libde265-0 along.

Apparently KDE distros with KDE Frameworks 5.80 have added support for HEIF and HEIC Image Formats to all KDE Apps (news, KDE announcement, MR), but the support flag is not enabled yet in the default (K)ubuntu packages (ubuntu bug).

Programs/Apps that support HEIF via libheif1 include:

GNOME Image Viewer (Eye of GNOME - eog) is updated in Ubuntu 19.10 and later. (Thanks seanlano!) - if it does not work for you, see PPA tip below.
gThumb Image Viewer & Organizer 3.11.4+, in ≥ Ubuntu 22.04 (for older verstions see below)
Darktable, free open source photography application and raw developer (3.8+)
GPicView (0.2.5+), can be installed from the Software Center or directly from the project page. Thank you, adasiko.
digiKam (6.4+)
GIMP (2.10.2+)
Krita (4.2+)
gImageReader (Ubuntu 20.04+)
Kodi (free and open-source media player software application) with Add-on:HEIF image decoder
xviewer (based on Eye of GNOME) with heif-gdk-pixbuf
Shotwell (0.32+)
Geeqie (1.6+) in Ubuntu 22.04
heif-thumbnailer - a thumbnailer for HEIF images that can be used by Nautilus and Nemo.
libheif-examples – provides command-line utilities: heif-convert and heif-enc.

I had these file emailed to me and used Krita to convert them.