Perhaps an interesting younger option. Still not super established so not quite an impact add. But younger still with some upside to build with. Someone of that general profile may be where to target. Chychrun is more established and still hasn't moved. Ottawa is looking for stabilizing vets so maybe there's a fit. That still seems like the best trade fit, although one with longer-term risk for durability reasons assuming he's extended.
Not too much else among RFA defensemen likely to shake loose. Maybe Durzi if Utah continues to make additions and he gets squeezed out.
I could see them adding one fourth-liner but less so two. They do have a long list of options that can compete in camp. I also thought Rybinski was more versatile and impressive all-around than Trineyev (esp. offensively). Definitely would wager they're going to want a greater degree of reliability and proven PK pedigree to replace Beck, though. Sutter could perhaps do it but I'd still hedge given just how big of a role Beck played.
Edit: Some other D trade possibilities that come to mind: Mike Matheson, MacKenzie Weegar, Torey Krug, Neal Pionk, Darnell Nurse, Ivan Provorov, Nick Leddy, Eric Gudbranson and Cody Ceci. Quite a few marginal at best upgrades, though.