I don't know Pern, but it seems you are describing teleport in a more defensive way. Couldn't linked portals work for summoning heroes to key strategic positions? Why give the heroes the ability to teleport offensively? What is the gain for the story? Because it brings up the huge story and setting problem as to why people bother with defensive strongholds at all.
I don't recall either situation, no, but I could stand to be corrected. The point is, that Gandalf didn't simply teleport Frodo to Mt. Doom and have him drop the ring in so they could be back to the shire in time for tea. So we didn't miss all of the sights and events of the Lord of the Rings. The problem with teleportation is that you don't have a reason to take a flaming chariot, a Griffon, or a Lord of Horses. You miss the journey because you just handwave everyone to the dungeon. If the DM wants to do that, he can simply say "after many miles, you reach the "temple of naughty baddies". Otherwise, it is an immersive breaking handwave from one fight set-piece to another, and contributes to the problem of going nova, teleporting out, buffing up again.
Linked portals are an elegant solution that doesn't require.
1) The DM putting anti-teleport wards on everything.
2) Screwing over the players (sometimes randomly) for daring to use a spell that they invested character resources and spell slots in.
Which pretty much every other suggestion on this thread requires. We have a solution, it pretty much works for all high-fantasy games (and doesn't intrude on low fantasy ones unlike the teleport spell). I'm afraid I just cannot see the downside to linked portals that makes people want to reach for that spell again.
The feather fall spell simulates that much better. For one thing, once they land, they land.