Any app on Ubuntu to open and/or convert HEIF pictures (.HEIC, High Efficiency I...

A certain cellphone maker has changed the default format of taking pictures to HEIF (.HEIC, High Efficiency Image File Format), without asking the users (although there is still the option to use jpeg/jpg).

Is there an app/program on Ubuntu that can open and/or convert HEIF-pictures and even let them be edited?

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