On Ubuntu 18.04 you can
sudo snap install gimp to get the latest version (2.10.
8 as of March 2019) which can open and edit HEIC files.
On Ubuntu 18.04 there's also a commandline tool to convert HEIC:
sudo apt install libheif-examples
heif-convert IMG_1605.HEIC IMG_1605.jpg
NOTE: you must use lowercase
.jpg or it will complain that it doesn't recognise the file format. That message is almost as misleading as the package name, and I can easily understand given these two papercuts why so few people have figured out how to use this tool.
For anyone who doubts that this is an official Ubuntu package:
user@host:~/Desktop$ dpkg -s libheif-examples
Status: install ok installed
Maintainer: Ubuntu Developers <email@example.com>
Depends: libheif1 (= 1.1.0-2), libc6 (>= 2.14), libgcc1 (>= 1:3.0), libjpeg8 (>= 8c), libpng16-16 (>= 1.6.2-1), libstdc++6 (>= 5.2)
Description: ISO/IEC 23008-12:2017 HEIF file format decoder - examples
libheif is an ISO/IEC 23008-12:2017 HEIF file format decoder. HEIF is a new
image file format employing HEVC (h.265) image coding for the best compression
ratios currently possible.
Sample applications using libheif are provided by this package.
Original-Maintainer: Debian Multimedia Maintainers <firstname.lastname@example.org>
OK so now the punchline of this joke. ;-)
You can use fuseflt or yacufs FUSE filesystems to mount your pictures folder with automated temporary cached conversion of your HEIC files so all the stock Linux desktop apps can open the HEIC files without ever knowing they're doing it.
Mark Deven below says that he only needed to install
libheif via aptitude to get these commands, though he didn't mention what distro he's running.