Sometimes strongholds get cut off by other underground structures (eg. ravines, mineshafts, etc.) there will be a stronghold, but sometimes, rarely, it won't even contain one room (eg. library, jail cells, etc.) the chances are really rare but its possible. the stronghold is basically useless. period.

Eyes of the ender are useless for locating the end portal inside a stronghold:

In Java Edition, the eye leads to near the spiral staircase that was the first room generated in the stronghold.

In Bedrock Edition, eye of ender signal leads to 5 crossing room that was the second room generated in stronghold.

In Legacy Console Edition, a thrown eye leads to a stronghold, but not exactly to an end portal.

While it is rare, it's possible in any version of Minecraft that the portal room got overwritten by a cave, a ravine or a mineshaft (even in Java Editions, where strongholds initially always generate with an end portal), in which case you have no other option but to find a different stronghold.

Strongholds don't necessarily have a end portal.

Here are some quotes about it:

There's usually 3 strongholds per world and they don't all necessarily all have a portal
_{^{- Stronghold without end portal - Minecraft Forums}}

After doing some more digging i found out that Java doesn't always have portals and Bedrock occasionally produces strongholds without portals:

There doesn't appear to be a portal at this stronghold. Although Java always has portals, Bedrock occasionally produces strongholds without portals.
_{^{- Strongholds with no end portals - Reddit}}