I've had a couple of seeds in which the portal is hard to find, but in this seed, I noticed that the stronghold was exceptionally small. I cleared the stone from the area with commands, then reset the chunks & used MCC Tool Chest PE to remove all stone, water, & waterlogged blocks (as well as replacing the stone brick with transparent glass). The world has the seed 4036522245, rendered as "-258445051" in the in-game world settings. The /locate command & ender eyes point to x= -4462, z=1968.

If you wish to see the world unedited, use either seed string & travel to the coordinates -4462, 62, 1968. Then mine down & you will find the corner of the stronghold, which exposes some stone. Notable features include the spiral staircase, a 2-story library, a hallway chest, & the stair-crossroads bridge-tunnel thing. No portal room is found, even with all other blocks removed. Although there is almost certainly another stronghold with a portal room, this is not helpful to most players. They may have travelled thousands of blocks outside their base to find little more than stone bricks & bookshelves.

I also used Universal Minecraft Editor to take the file size from 15.1 MB to just 4ish. All I did was trim some chunks & delete unnecessary data. Again, to see the world as it was originally generated, you can open a new world from the seed or reset the chunks of the world download.