Just following up here from a Slack thread regarding some self-inflicted problems I encountered related to this update. I had slightly different problems on two different systems (why have one when you can have two?), but both were related to have old registries in various directories of DEPOT_PATH.
On the first system, I had an old-but-renamed copy of the General registry in my ~/.julia/registries directory. That was easily cleared by by removing that old, unwanted clone.
In the second system, it turns out I had old General.toml and General.tar.gz files in one of the system-wide DEPOT_PATH directories. This was causing some confusion (for both me and Pkg apparently) such that the OpenSSL_jll version caps were not being recognized/honored so packages like FFMPEG_jll couldn’t load (which broke Plots!). Part of the confusion was caused because ]registry status only showed one General registry even though I had two different sets of General.toml and General.tar.gz files on DEPOT_PATH. Removing the older set of files (from the system-wide depot directory) resolved the problem.
Thanks go to @mkitti and @giordano for helping me get to the bottom of it!