The NUC and Optiplex aren't bad either. There are also very good AsRock boards (I can't remember what the modern ones are called but H110T is one, I used this for a bit, idled at 6W, laptop memory and power brick). But Fujitsu is the S-tier.

In practice, I found I needed a bit more power but you can get some of the Fujitsu boards with a CPU for $30-40, which is hard to beat.

I have a HP ProDesk powertop shows up to C10 which I never reach. Must be the SSD or NVMe I have. But yeah The BIOS in those are super cut down and there are hardly any energy settings I can change.

fujitsu has always been underappreciated in the mainstream tbh. there has always been a thinkpad-style cult following (although much smaller) but japanese companies often do a pretty terrible job at marketing in the west (fujifilm being another fantastic example).

my university issued T4220 convertible laptops, with wacom digitizers in the screens. I rarely used it but the pivot in the screen made it indestructible, it survived numerous falls hitting the corner of the screen/etc because the screen simply flops out of the way and pivots to absorb the energy. I later got a ST6012 slate PC that my uni bookstore was clearing out (also with a wacom digitizer, and a Core2Solo ULV!). Both of them are extremely well-thought-out and competently designed/built hardware. Doesn't "feel" thinkpad grade, but it absolutely is underneath, and featured PCMCIA and bay batteries and other power-user features.

https://www.notebookcheck.net/Fujitsu-Siemens-Lifebook-T4220...

https://www.ruggedpcreview.com/3_slates_fujitsu_st6012.html

They also did a ton of HPC stuff for Riken and the other japanese research labs, they did a whole family of SPARC processors for mainframes and HPC stuff, and pivoted into ARM after that wound down. Very cool stuff that receives almost no attention from mainstream tech media, less than POWER even.

https://www.youtube.com/watch?v=m0GqCxMmyF4

Anyway back on topic but my personal cheat-code for power is Intel NUCs. Intel, too, paid far more attention to idle power and power-states than the average system-integrator. The NUCs are really really good at idle even considering they're using standalone bricks (my experience is laptop bricks are much less efficient and rarely meet 80+ cert etc). A ton of people use them as building blocks in other cases (like HDPlex H1 or Akasa cases), they don't have a ton of IO normally but they have a SATA and a M.2 and you can use a riser cable on the M.2 slot to attach any pcie card you want. People would do this with skull canyon f.ex (and HDPlex H1 explicitly supports this with the square ones). The "enthusiast" style NUCs often have multiple M.2s or even actual pcie slots and are nice for this.

https://www.amazon.com/ADT-Link-Extender-Graphics-Adapter-PC...

And don't forget that once you have engineered your way to pcie card formfactor, you can throw a Highpoint Rocket R1104 or a SAS controller card in there and run multiple SSDs (up to 8x NVMe) on a single pcie slot, without bifurcation. Or there are numerous other "cheat code" m.2 devices for breaking the intended limits of your system - GPUs (Innodisk EPV-1101/Asrock M2_GPU), SATA controllers, etc.

https://www.youtube.com/watch?v=M9TcL9aY004 (actually this makes the good point that CFExpress is a thing and is very optimized for power. No idea how durable they are in practice, and they are definitely very expensive, but they also might help in some extreme low power situations.)

Personally I never found AMD is that efficient at idle. Even with a monolithic apu you will want to dig up an X300TM-ITX from aliexpress, since this allows you to forgo the chipset. Sadly AMD does not allow X300 to be marketed directly as a standalone product, only as an integrated system like a nuc or laptop or industrial pc, despite the onboard/SOC IO being already quite adequate for beige box usage. Gotta sell those chipsets (hey, how about two chipsets per board!?). But OP article is completely right that AMD’s chipsets just are not very efficient.