I don't think gnome-photos was removed from the repos, I think it was just removed from the ISO.
gnome-photos package is not installed
Package found in Solus repository:
Name : gnome-photos, version: 3.38.0, release: 43
Summary : Access, organize, and share your photos on GNOME
Description : A simple application to access, organize and share your photos on GNOME. It is meant to be a simple and elegant replacement for using a file manager to deal with photos. Seamless cloud integration is offered through GNOME Online Accounts.
Licenses : GPL-2.0-or-later
Component : multimedia.graphics
Dependencies : libgdata libjpeg-turbo babl pango libgtk-3 libdazzle grilo gexiv2 libcairo gfbgraph glibc libgeocode-glib gegl gdk-pixbuf tracker gnome-online-accounts libatk libpng glib2 grilo-plugins
Distribution : Solus, Dist. Release: 1
Architecture : x86_64, Installed Size: 3.48 MB, Package Size: 622.00 KB
Reverse Dependencies: gnome-photos-dbginfo