You have been able to access your Instagram account from a desktop browser for quite some time but you cannot post a photo without a workaround. The workaround is quite straightforward. You simply log into Instagram on your desktop browser, switch to developer mode (right-click “inspect” in Chrome) and choose a mobile device view. Full instructions are here.
I just tried it successfully with my recent kingfisher photo…seems to have worked. Saves me having Instagram running on my phone as it drains the battery really quickly even with the app supposedly “inactive”.
Developer or “inspect” mode in Chrome lets you make your browser look like it’s a mobile browser running on a Galaxy, Nexus, iPhone, iPad etc. If you want to see what a site looks like (perhaps testing your own for instance), this is a useful tool. I’m sure there are mobile only sites out there that people use, this is a workaround for that too, so you don’t have to use an actual mobile device. (I assume it’s simply doing a user-agent switch within the dev mode, which reverts to normal browser when close the dev window). It’s a tiny bit more complicated for Safari on a Mac, but the instructions are in the link