So this happens to me too and to the owner of the realm.
The owner refreshed the realm to the previous saved back up and was able to go in but I still cant join. The realm would load and then says "Let's go!" and minecraft would crash.
I tried joining on phone after and the same thing happened.
so far I've logged in and out of my microsoft account, completely left the realm and tried to join back in, installed and reinstalled the game and even restarted my computer.
Other friends on that realm seem to have no problem joining, so far only i have this issue and it only occured after the update (now using v1.16.220)
the steps are there, dig down until it crashes and being in water for a while til it crashes, those are literally what i did, I dont know how else to say it. Press rt and aim down??
the issue is only with 1 person in my realm while 4 others are fine and have no problem, logging in crashes the game and exits the applications.
I paid for a realm to play with them but they can't join, so clearly, this issue isn't resolved or being helped