If you really want to do Web uploads on Instagram, you can do it using Chrome.
When you're signed in to your account, right click the page > inspect. Then when the right side inspect panel opens, make sure "device tool bar" is toggled to show up (it's an option in the very top right, left of Elements, Console, Sources, etc).
Set the device options to responsive, something like 500x700 or whatever works for you. You can drag the dimensions on width. Then reload the page. It should retain the device dimensions choice and will show the mobile nav bar at the bottom that includes an upload button.
When you're signed in to your account, right click the page > inspect. Then when the right side inspect panel opens, make sure "device tool bar" is toggled to show up (it's an option in the very top right, left of Elements, Console, Sources, etc).
Set the device options to responsive, something like 500x700 or whatever works for you. You can drag the dimensions on width. Then reload the page. It should retain the device dimensions choice and will show the mobile nav bar at the bottom that includes an upload button.