Minecraft old world updated, just a stronghold?

I updated my old minecraft world a few days ago. Yesterday I made it to the end stronghold and went to the end. Dragon defeated, all right. Until I noticed that there's only one island. No other islands where I elytren o.ä. Can be found. I also looked for other strongholds, but all pearls have led to the same stronghold. Can someone explain why there are no other islands and how to proceed?

PS: My Minecraft version is up to date.

If you kill the dragon, a portal will spawn on the edge of the island.

If you throw in an Enderperle, you will come to the other islands.

Thank you so much! I'll try it out.

You can also build there, but then you need about 2000 blocks.