It appears that Instagram has killed off or deactivated the web-based portion of their Explore feature.
As of now, any tag or location link accessed is returning a 501 error. Many users on Twitter are reporting the issue and judging by timestamps it seems like the issue began roughly 20 hours ago. Instagram has not commented on this issue and has not been replying to users mentioning the problem on social media.
It is possible that this may be server issues or it may be a strategy taken by Instagram to either reduce inauthentic and automated behaviour or test if the outage decreases these activities.
Will keep you posted on any new developments.
Edit: September 16, 2020
Looks like the issue has been addressed and tags and locations are now working again.