JPEGView is your go-to. Not only is it incredibly minimalistic and lightweight (even portable), but it allows you to almost instantly view any image in full resolution, switch to next or previous images within the same folder, quickly zoom in with scroll or fit to screen with space, and has a built in editor for adjusting contrast, brightness, hue etc..
It also solves your problem with switching images after zooming in if I'm not mistaken.
I've been using it for a few months after having the same issues as yourself with the default image viewer and It's completely replaced it.
If you look at this satellite photo, this is the last area they pass through before their bones are found, so they either they passed that very area alive, and it looks like quite a dangerous rocky area, or they got washed downstream as bare bones. But also it looks alot like a waterfall and there's no way that bag isn't getting wet inside.
https://imgur.com/gallery/xc1P89h
** Use jpegview - https://sourceforge.net/projects/jpegview/ **
Jpegview is the fastest, most minimalistic image viewer I have ever used. It's beautiful and fantastic. It's also free and open source! *^not ^a ^paid ^endorsement
How is the update going?
I've just discovered an image viewer that covers most of my needs while waiting for further developments on your software.
JPEGview can me made to work with .lep with a bit of a workaround. I haven't tried it myself, but should work.
It's a bitch. In regards to jpg and png Chrome may still display webp regardless of extension in URL, but if you right click and press Save As you might still be able to save images in original format, assuming they're available on server alongside webp version.
As for gif--if it's not available on server you'd have to either convert it or just get an image viewer capable of displaying webp; JPEGView works for me.
I've been looking for a way to disable webp in Chrome altogether. If anyone knows one, I'm all ears.
Android: Simple Gallery/Snapseed
Windows quick and easy:
jpegview
Does way more than jpeg, including raw files, and includes simple editing tools.
For something more advanced I would look into darktable. Pretty sure they have a windows client.
Photo viewer is JPEGView, by the by; one of the best I've found for MS Windows Wallpaper is this image with some color splashed around it