Another long term fix is to consider using https://heiconvert.com to easily convert your HEIC images to a more compatible format, making them accessible in your default Image Viewer on Ubuntu. It's a quick solution for hassle-free image viewing.

In recent Ubuntu versions (>= 18.04):

sudo apt-get install libheif-examples

And then

for file in *.heic; do heif-convert $file ${file/%.heic/.jpg}; done

In older Ubuntu or Mint versions, first add this PPA and then do the above steps.

sudo add-apt-repository ppa:strukturag/libheif
sudo apt-get update

For local conversion, this worked for me in Debian. Just downloaded the static build, ran the example conversion command, everything worked:

https://github.com/monostream/tifig

This heic combined still + video burst file opened in mpv

IIRC they’re Apple’s implementation of high quality images? I just converted them to JPEG, but a quick google search has pointed me to this tool: heif-gdk-pixbuf Now I’ve not used this so cannot confirm if it’s any good, but it might be worth checking out.