This issue appears to apply to the MongoDB website login as well as one of the bigger clients MongoDB has, humanitix, so it is not an isolated problem.
The issue appears to apply only to the Safari browser on desktop where a user checks the box in their Safari settings: “Block all cookies”. I am on Safari 16.2
Basically, my website refuses to load on this browser, and I have traced it simply to the use of MongoDB Realm on my website. Now, the immediate problem is not that MongoDB Realm refuses to work on this browser, but that the website is not allowed to load at all, so I am not able to provide a message along the lines of “Sorry, this website requires cookies to function.” The user is left in the dark as all that shows up is a white screen. Even the console does not offer any error message.