Having written a story about how Instagram was replacing the original app in the Store with a simple web wrapper on a PWA implementation, the next step is obvious and apologies it has taken me a few days to realise and test it, but... never mind the app, never mind third party UWP apps like Winsta, the full Instagram experience is now up on instagram.com. No installation needed, no messing with Store compatibility or landscape mode. Just pure Instagram in (here) an Edge tab. It 'just works'.
It should be noted that Instagram has presented pretty well on the web in recent years, with a subset of the full 'experience', but to my knowledge this is the first time that everything has been up and available from any compatible web browser with zero effort. And yes, this includes Edge under Windows 10 Mobile. See the walkthrough here and be (relatively) impressed.
Nothing to see here, just Instagram. But in Edge and not a cut-down, minimalist view. And no need for landscape mode or clumsy hacks. It's a PWA and available on the main URL, here with a post from our illustrious site owner and his dad, and starting to browse Rafe's Instagram profile... (Sorry to make you blush, Rafe, but people like knowing what you're up to, and it's all public!)
Swiping down to see Rafe's posts in image form, and then clicking through to find out that he secretly likes BlackBerrys (cough)...
Starting a new post/story, there's a full camera-based UI (here on a Lumia 950), with graphical effects and flags that can be superimposed...
...as here, just drag to where you want them and release. Ditto any text you want to add, in any font or colour....
Then it's on to Instagram's traditional photo filters, before adding a caption and bang, your story/feed item is done.
You won't necessarily want to go via Edge and the Favourites menu each time, of course, so note that you can just pin Instagram.com to your Start screen, the 'favicon' gets picked up and it doesn't look unattractive.
If you do 'pin to Start' then note that tapping this tile starts a new browser tab, so if you know that you already have Instagram open in a tab then it's more resource-efficient on your phone to go via Edge and switch to that tab. We've all seen 'normobs' with a billion tabs 'open', unwittingly, so don't be that person with ten different tabs open to the same instagram.com URL!!
It's trivial to see all this for yourself under Windows 10 Mobile, in any case. Just go to instagram.com in the Edge browser and get started!