"KuickShow is an image browser/viewer with a nice filebrowser to select images to be shown, slideshow support and the ability to display the following image formats: jpg, gif, tiff, png, bmp, psd, xpm, xbm, pbm and eim. Images can be displayed either in their own window, as large as the image, or fullscreen (which shrinks images too large to display). KuickShow also has a slideshow mode."
... free, open source image viewer, which supports multiple platforms. You can use it for viewing all common image formats including RAW and psd images.
You may like Kuickshow.
"KuickShow is an image browser/viewer with a nice filebrowser to select images to be shown, slideshow support and the ability to display the following image formats: jpg, gif, tiff, png, bmp, psd, xpm, xbm, pbm and eim. Images can be displayed either in their own window, as large as the image, or fullscreen (which shrinks images too large to display). KuickShow also has a slideshow mode."
XnViewMP is very good doing the job.
Download it from http://www.xnview.com/en/xnviewmp/
Nomacs is a fast and easy to use program: https://nomacs.org/
Edit: From the Nomacs landing-page its a:
Screenshot:
For simply previewing PSDs I use ImageMagick - fast and displays them properly. Also it's free and available via apt.
Besides Photoshop, I believe GIMP is your best option. Might be the closest to Photoshop.