Cannot access GitHub on MacBook using personal hotspot from iPhone

I encountered a very strange problem that I couldn't find anybody ever reported anywhere using Google.

On my MacBook using my iPhone SE's personal hotspot, it is almost not possible to access GitHub. It may work once at the beginning (i.e. the first connection), then "Safari cannot find the server", and after waiting for 15-20 minutes, it may work again.

Some important observations:

• The issue does not happen for any other websites than GitHub.

• On the iPhone, it works. Thus the phone's 4G connection is not an issue.

• Using another iPhone (6S) with another 4G network (different carrier) as personal hotspot, it works.

I've desperately searched for a solution on Google but it seems nobody ever had the same issue.

Could you please help? Thank you very much in advance!

Solution 1:

It was an DNS issue (thanks to @jsbillings for pointing out). Using Cloudflare's DNS is a workaround.