nomacs is a free, open source image viewer, which supports multiple platforms. You can use it for viewing all common image formats including RAW and psd images.
qView is a Qt-based image viewer designed to be practical and minimal, available for Windows, macOS, and Linux
qView vs ImageGlass opinions
Open source, cross platform and minimalist.
Xee is an streamlined and convenient image viewer and browser. It is similar to macOS's Preview.app, but lets you easily browse the entire contents of folders and archives, move and copy image files quickly, and supports many more image formats.
Easily gather, organize and protect all of your photos across all your devices. Use Mylio to rediscover, enjoy, and share your memories—anytime, anywhere.
Picturama is a free and open-source image organizer for the desktop built on Electron and powered by web technology.Discontinued
the latest release is build in 29 Sep 2020