Microchip bought Atmel and they now have the SAM controllers. I came here to ask questions as I am sure there is more knowledge about SAM parts here than on the Microchip forum.
There's also the previously-existing
Atmel Smart ARM Community. YMMV; it seems somewhat less than helpful (more questions than answers.)
Assorted "Modern" Arduino-like boards have SAM procssors Arduino Due is a SAM3x, Arduino Zero (and many similar) is a SAMD21 , Adafruit has the "Metro M4" with the new SAMD51. None of these have ethernet at the board level (SAM3x has an ethernet Mac on the chip, but they didn't add the Phy or connector.)https://www.microchipdirect.com/product/search/all/ATSAME54-XPRO is probably a good board with ethernet, at the high end.
I'd generally rate the Atmel "roadmap" for the SAM processors as a bit "confusing." They stretch from Unix-capable Cortex-A chips to 14-pin CM0+ chips, and it's a bit difficult to gauge where their attention is. SAM3X is already NRND, and Atmel had ARM7 and ARM9 chips as well. OTOH, this tends to be a problem with most ARM chip vendors; and ARM themselves - there's always a new core in the pipeline with important new features... (OTOH, I'm just a hobbyists, so I haven't had the opportunity to quiz Microchip management on their intents. General opinion seems to be that getting a jump-start on ARM was one of the reasons that they acquired Atmel in the first place.)
The "Xplained Pro" boards are pretty nice development boards with a relatively powerful built-in debugger.The "Xplained Mini" boards have a slower debugger chip, and are much cheaper.