Why? Is there some workarounds to add a link to an individual post?
No, but you can
There is an Instagram Chrome Extension that converts links to clickable links.
I thought about QR code, but yes, it will require an onscreen QR code reader.
Another thing, which I started exploring is to have an actionable image. There is a hack that allows adding JS script into an image, but I am not sure if a) It will ever be allowed on Instagram, b) it actually works the way I wanted.
Instagram wants you to stay in Instagram, this is the primary reason they don't allow links in posts. I believe the closest you can get to what you're looking for is a swipe-up link on a story. This feature becomes unlocked when you've reached 10K followers. For posts, I believe you're stuck with the standard "see link in bio" within the post caption.
Yeah, I know about see link in bio, amazing, some companies even offer Instagram like design when a user clicks a link.