gThumb is highly recommended for users who need a reliable tool for managing photo collections and performing basic edits. It’s particularly suited for those using GNOME-based Linux distributions and anyone seeking a no-frills image viewer with additional editing capabilities.
XnView MP is recommended for photographers, graphic designers, and anyone who needs to organize, view, and edit a large collection of images. It's also well-suited for users who require bulk processing and conversion of image files.
XnView MP stands for Multi Platform = it is available for Windows, Linux and MacOS. It is a continuation of the older XnView Classic. In my opinion it is a great alternative to Windows photos app or any Linux image viewer that comes preinstalled. I even think it is an alternative to IrfanView. It is really fast and simple to use, supports more than 500 image formats, has built in folder browser, image converter, editor... AND MORE!
IrfanView - IrfanView ... one of the most popular viewers worldwide.
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
JPEGView - JPEGView is a small and fast viewer/editor for JPEG, BMP, PNG, GIF and TIFF images.
nomacs - nomacs is a free, open source image viewer, which supports mu
digiKam - Professional Photo Management with the Power of Open Source
Gwenview - Gwenview is an image viewer for KDE.