I've been looking for a good SFF home server system but every one I find has an external PSU. It's surprising to me. I'd love an Intel NUC but I don't want a power brick the size of the computer itself.
In case you don't already know, the Mac mini has an internal PSU.
I'm like you; I want one box / lump, not two (mainly because I move the box around a lot). Consequently, I have a Mac mini. The price cheapest non-used Mac mini however has risen from $500 to $800 in about 3 years.
It also overheats if you use it for too long (e.g. keep the Simulator open for most of a work day), causing the machine to slow down to a barely usable speed.
This seems to be a common thing with apple devices - supposedly powerful hardware with woefully inadequate cooling. iirc one of the i9 macbook models actually performed worse than the corresponding i7 model because the cooling was so bad.
Never could figure out people who actually wanted an internal PSU ... i thought big tech forced them on us for reasons of their bottom line: Ie as planned obsolescence. Eg one could easily make a svelte "phone" with a 30 second capacitor and Qi power transfer... Such would not wear out, letting one choose, swap, power backs/cases. Bigger things might standardize on wired connections like USB-C to cheap 18650 packs.
There are options for building a brickless SFF system, but they all have tradeoffs or limitations. There isn't a good one-size-fits-all internal psu until you get to the SFX size psus.
I myself have been building out a brickless skyreach s4 mini system inspired by this [0] (same author as this A300 unboxing)
Honestly, if there was a way to attach them together (say, a clip), I'd be fine with a brick. Make the clip provide a small gap and airflow should be good enough to prevent thermal issues. If I do run into problems, I can always separate them...
I'm like you; I want one box / lump, not two (mainly because I move the box around a lot). Consequently, I have a Mac mini. The price cheapest non-used Mac mini however has risen from $500 to $800 in about 3 years.