Current mysteries in game?

What are the current mysteries, now that odyssey is out?

I have a little over 4500 hours, and been playing since about day 10 from game release. I have had several reddit accounts in that time, and was previously known for trying to protect players from the worst of the worst player pirates (eg protecting distant worlds from well known gankers)

I have multiple accounts, and one is a prolific explorer by the name of Beng Ammon ( pronounced 'been jammin'), Raxxla hunter, and Elite story progressor. I have a fleet carrier, named after an obscure scifi movie from the 80s, and almost all of the bubble engineers unlocked.

These are the mysteries I know about:

1) Raxxla.

Been confirmed for years as "in game" from braben himself, with little other clues.

2) gen ships

Not all generational ships have been found

3) Unregistered comms beacons

There are 10-20 (maybe more?) Unregistered comms beacons still to be found

4) the thargoid base that lights up a map has been figured out, and preodyssey, led to a part of space that was "locked" off.

5) guardians and it's AI Construct.

Through a slogfest of Ramtah missions, you can unravel the guardian mystery, at some point it just stops.

6) the new mystery around the Alexandar ship.

So question commanders:

What's the mysteries I'm missing?
Any development on guardiansAI story?
Anyone find new comms beacons?
Anything new from the code sleuths that could help us in the right direction? (Since fdev has chosen to keep lips sealed on just about everything)

Any help would be appreciated.