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!
digiKam - Professional Photo Management with the Power of Open Source
IrfanView - IrfanView ... one of the most popular viewers worldwide.
ACDSee Photo Studio - ACDSee becomes ACDSee Photo Studio — ACDSee Photo Studio Standard 2018 continues the ACDSee legacy
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Shotwell - Shotwell is an open source photo organizer designed for the GNOME desktop environment.
JPEGView - JPEGView is a small and fast viewer/editor for JPEG, BMP, PNG, GIF and TIFF images.