gThumb

An image viewer and browser utility for the GNOME environment.

Scale to fit:

App ID:

org.gnome.Photos

automatic-app-scaling

Phone Compatibility:

4 of 5 Points, with scale-to-fit. You may also need to manually run tracker with tracker daemon -s

How to install:

APT:
sudo apt update
sudo apt install gnome-photos
Flatpak:

Flathub: https://flathub.org/apps/details/org.gnome.Photos

Command:

# You will need to trust and add flathub to flatpak
flatpak install flathub org.gnome.Photos

Repo: