Hi @danieldoughty,
Thanks for spreading the word !
To be exact you can't actually post on Instagram via a classic web browser on PC... in theory.
But there's a trick !
Right click on the page and chose inspect, then, on the inspector, click on the tablet/smartphone icon. The layout changes into mobile website.
Now refresh the page and TADA ! You're now on mobile interface with the post button ! You can now post on Instagram via a classic browser...
wow.. thanks for the info.. hehe . learning something new everyday