I'd just make a couple of points that stand
out to me from the discussion.
If the attacker isn’t getting that ball then 100% not a penalty unless the keeper is judged to have endangered the opponents safety or used excessive force.
Endangering an opponent or using excessive force are not the only ways to commit a foul - there's also careless and reckless to be considered. In any event, it makes no difference whether the player was going to reach ball or not - so long as the ball is in play when a potentially illegal action occurs, an offence is still possible.
looked at that and the only possible offence was "tackles or challenges" but i couldn't work out what this really meant.
"Tackles or challenges" is not an offence in and of itself - only if it's careless, reckless or uses excessive force.
Also, and in case it helps, the LotG Glossary gives definitions of both terms.
Tackle
A challenge for the ball with the foot (on the ground or in the air)
Challenge
An action when a player competes/contests with an opponent for the ball
Another possibility is "trips or attempts to trip."
How can a careless foul be given with no contact at all?
Well, if a challenge with no contact at all can be judged reckless and worthy of a yellow card (I'm sure we all remember the Wayne Rooney incident where this happened) then I'm pretty sure we can also have a careless challenge without any contact.
Anyway, based on the referee's quoted comment of, "if the attacker hadn't jumped the keeper would have cleared him out," it sounds entirely possible that this challenge by the keeper was reckless, although of course it's difficult (if not impossible) to say without having seen it.