could't open firefox

What I would check first: does any file exist somewhere that starts with gdk_pixbuf-2 ?
If found, make a symlink /usr/pkg/lib/libgdk_pixbuf-2.0.so.0 to it.
In case not, try reinstalling graphics/gdk_pixbuf2...

MG_ Randomly adding symlinks is just going to be a mess sooner or later.

It's fine to use it to investigate a concept but, it's not a solution to the problem.

On my system:

~ $ readlink -f /usr/pkg/lib/libgdk_pixbuf-2.0.so
  /usr/pkg/lib/libgdk_pixbuf-2.0.so.0.4200.6
~ $ pkg_info -Fe $(readlink -f /usr/pkg/lib/libgdk_pixbuf-2.0.so)
  gdk-pixbuf2-2.42.6nb1
~ $ pkg_info gdk-pixbuf2
Information for gdk-pixbuf2-2.42.6nb1:

Comment:
Library for image loading and manipulation

Requires:
shared-mime-info>=1.0nb1
glib2>=2.70.2
tiff>=4.0.3nb5
png>=1.6.0nb1

Required by:
gdk-pixbuf2-xlib-2.40.2nb1
gtk3+-3.24.33
gtk2+-2.24.33nb4
dunst-1.5.0nb2
librsvg-2.52.8
libnotify-0.7.9nb4
dino-0.3.0

You can use pkg_delete -f gdk-pixbuf2 to force remove it, and then attempt to reinstall it (either as binary package, or by building it from source). I'd clear the pkgin cache first in the former case. Use pkg_admin check and pkg_admin rebuild to get an idea of what's going, by displaying missing shared objects and file checksum mismatches system-wide. Remember never to mix different pkgsrc branches.

pfr What did you do here?

I don't think firefox will be the only package that is broken. If/when updating textproc/icu across major versions, you need to rebuild every singel package that has any, direct or, indirect dependency on it.

If you are using precompiled binaries, chances are the build took place in between the icu update and the required REVBUMP of all dependencies.
In which case, you need to wait for the next bulk-build in order to get this sorted out.

pin you need to wait for the next bulk-build in order to get this sorted out.

Thanks. You must be right.

I uninstalled firefox and tried to reinstall and now I get

firefox is not available in the repository

pfr You must be right.

There were quite a few breaking updates in a rather short period of time. Changes to Python, OpenSSL, default Go version, icu and cairo. But, given the output you showed above, it's clearly icu.

MG_ What if it works?

Then that's a good thing. You you are putting your system into an unexpected state though, which might confuse automated administration tools (like package managers) later on.

pfr what does 'pkgin avail | grep -I firefox' net?

kc9udx
The only result is

firefox_decrypt-0.7.0nb3 Extract passwords from Mozilla Firefox profiles