We’ve had the fiber trunk line run through the back yard for 6 months or so. Luckily they have called and installs are running 4 to 6 weeks out at the time they called.
Feel very lucky fiber is even go an option. We are a good 3 miles from the closest town of 25 or so houses and 20 miles from the nearest city where the fiber originates from. It’s a joint venture with a small company and our electric utility.
I’d replace the post.
The foam might work for a hot minute but I’m not even convinced of that. I’d think the stress from the weight of the gate will cause it to fail rather quickly.
If the hollow is up in an area where the hinges attach you might split the post with the foam expanding as it cures.