The summary explains it all, really.
Seed is 347815779, and the stronghold is underneath a village nearby. It leads to an area near-ish the stronghold and hovers in place underground before dropping. The stronghold has no ender portal as far as I can tell, especially not anywhere near the portal.
Thank you for your report!
However, this issue has been closed as a Duplicate of MCPE-19426.
Please add a vote and any new information to the main ticket, which will be updated accordingly.
If you have not, you might like to make use of the search feature before making a new ticket, as it's likely that the issue has been reported already.
Quick Links:📓 Issue Guidelines – 💬 Mojang Support – 📧 Suggestions – 📖 Minecraft Wiki