How did the Archon gain control of...

Computer work based on numeric code.

But then that means that SAM's senses are not limited to Ryder's because SAM can see what is going on inside Ryder's body via the implant. If that's the case, I still question how the archon could have learned so much about SAM. SAM knew the archon planted that device in Ryder. I assume SAM neutralized it, after stopping Ryder's heart. The archon then learned everything about SAM through Ryder's memory flashes? How does one even "see" another person's memory flashes?

But then that means that SAM's senses are not limited to Ryder's because SAM can see what is going on inside Ryder's body via the implant. If that's the case, I still question how the archon could have learned so much about SAM. SAM knew the archon planted that device in Ryder. I assume SAM neutralized it, after stopping Ryder's heart. The archon then learned everything about SAM through Ryder's memory flashes? How does one even "see" another person's memory flashes?

But then he leaves the Hyperion, with the sib.  So clearly he didn't need all of SAM.

I still say the game is inconsistent with SAM'S abilities. When Ryder first encountered the archon on the way to Aya, archon takes control of navigation. SAM tells Ryder "*I* have almost regained control of the ship." On the first visit to Aya, without Ryder's scanner, SAM detects the energy levels in the angara, and analyzes the plants. Ryder cannot even use the scanner, bc the angara threaten Ryder with guns if he/she tries to use it.

Sam did everything edi did. If no one complain when edi hacked every thing why complain when sam does.

The Archon "shackled" SAM. For all its personality, SAM is an AI; and shackled AIs have no choice but to obey directives.

Of course SAM has sensors. It has ridiculously good perception through Ryder's hardsuit and omnitool, and likely some camera access in SAM node. It has no defenses, though. Most people are freaked out by SAM. They reticently accept that the Pathfinders use SAM, but aren't particularly comfortable with it. There's no way they'd allow SAM access to hardware with which it could battle "intruders", fearing it would possibly turn them against AI personnel. Once Hyperion falls under kett control, SAM is relatively defenseless against the Archon's shackling.

We have no idea just how intelligent Archon is, but he seems likely much smarter than Ryder. He's old, possibly very old, and thus pretty experienced. He has the genetic traits of who-knows-how-many species. His having the smarts to puzzle out Remnant tech isn't that shocking, to me. He's been studying this stuff for 80+ years. He has a grasp of how it works, but can't access it at all until seizing SAM.

More importantly, we learn after the fact that he wasn't even controlling the tech during the fight. It just seemed that way to Ryder. He was completely overwhelmed by the connection to Meridian. His snooping awoke the damaged Architect and its bots, but he wasn't controlling them.

I can't help him on the "being more interesting" front, since that's entirely subjective.  The other issues, though, actually make sense once all provided data is considered.

Yes!

And how did the archon *see* and interpret human flashes of memory (which if you slow down you can actually see that it's just Alec's memories of his family)?

How did the archon, from those brief memory flashes, have all the information required to shackle SAM (kett don't study AI they destroy it, so how does archon know how to work SAM when he's never studied AI before)?

How did archon know how to successfully use sibling Ryder's implant when the only knowledge archon has is either the memory flashes (which is just Alec's memories of family) OR the brief insight gained from planting the device in Ryder? (I don't accept that SAM just couldn't disable the device fast enough as an explanation, bc then the answer is SAM couldn't bc the plot demanded it.)

1) WHy isn't it hard?  Again, the kett don't utilize AI
2) Remember how hard it was for Shepard to decipher the Prothean beacon without a Cipher?  This seems to be quite similar in nature.
3) QEC connections can't be tracked.  That's a big part of their appeal: they are completely secure.