The "protect me from an attack" part of Lighthouse will not work when you have it inherited.
Lighthouse reads, in part (under the dividing line):
While you have this in play, when another player plays an Attack card, it doesn't affect you.
Notice the bold part, it only works when it is in play. If you have inherited Lighthouse and play an Estate, you have the Estate in play, not the Lighthouse. Due to the Fall 2019 errata, the Estate no longer takes on the abilities of the Lighthouse (as it used to do before), but "only" becomes an Action card that plays the set aside Lighthouse (the relevant part of Inheritance reads)
During your turns, Estates are also Actions with "Play the card with your Estate token, leaving it there."
So again, the (new since 2019) situation is that you have an Estate in play and a Lighthouse set aside, so Lighthouse does not protect you from your opponent's attacks, because its condition is not met :(
Lighthouse reads, in part (under the dividing line):
While you have this in play, when another player plays an Attack card, it doesn't affect you.
Notice the bold part, it only works when it is in play. If you have inherited Lighthouse and play an Estate, you have the Estate in play, not the Lighthouse. Due to the Fall 2019 errata, the Estate no longer takes on the abilities of the Lighthouse (as it used to do before), but "only" becomes an Action card that plays the set aside Lighthouse (the relevant part of Inheritance reads)
During your turns, Estates are also Actions with "Play the card with your Estate token, leaving it there."
So again, the (new since 2019) situation is that you have an Estate in play and a Lighthouse set aside, so Lighthouse does not protect you from your opponent's attacks, because its condition is not met :(