It does seem to me pretty clear though that if God gave those from before the Flood a chance at repentance and salvation through the gospel, then not showing favoritism, one could expect that some equal chance at repentance and salvation through faith in Christ could be expected then for any of the dead that had never heard the gospel, as they would presumably have an equal chance, there being no favoritism. (God would have no trouble bringing together souls from any time, as time is not an obstacle for the almighty.)
On the more complex and less fully known situation in regard to Hades and the possibility of 'purgatory' for instance, the Catholic doctrine, I've gotten the impression that even for Catholics that not very much is known about it past a couple of limited things, but perhaps someone could fill in more?
Here's what I know about that.
Anyone who has knees to bow and a tongue to speak, in heaven and on earth and under the earth (in the realm of the dead), will whole-heartedly, and without reservation, acknowledge that Jesus Christ is Lord. No one can say that “Jesus is Lord,” except by the Holy Spirit. If you declare with your mouth, “Jesus is Lord,” you will be saved. Christ died and returned to life so that he might be the Lord of both the dead and the living. (the reason for the bodily resurrection) Scriptures below.
Philippians 2:10-11
that at the name of Jesus every knee should bow,
in heaven and on earth and under the earth,
11 and every tongue acknowledge that Jesus Christ is Lord,
to the glory of God the Father.
1 Corinthians 12:3
Therefore I want you to know that no one who is speaking by the Spirit of God says,
“Jesus be cursed,” and no one can say, “Jesus is Lord,” except by the Holy Spirit.
Romans 10:9
If you declare with your mouth, “Jesus is Lord,” and believe in your heart
that God raised him from the dead, you will be saved.
Romans 14:9
For this very reason, Christ died and returned to life so that
he might be the Lord of both the dead and the living.
Note on "acknowledge" in Philippians 2:11 from Strong's Concordance
S1843 eksomologéō (from 1537 /ek, "wholly out from," intensifying 3670 /homologéō, "say the same thing about") – properly, fully agree and to acknowledge that agreement openly (whole-heartedly); hence, to confess ("openly declare"), without reservation (no holding back).
Further reading: (
Isaiah 45:23,
Romans 14:11,
Philippians 2:10,
Revelation 15:4)