I have heard lots of people saying this, actually.
I did not immediately realize the importance of your "multiarch" comment (especially for us here at Armbian!), until I was reading something at r/docker about someone who was trying to use x86 container on ARM which of course is not going to work. As containers are, after all, just some upper part of filesystem overlay + some isolation, but still relying on underlying hardware of course.
I went to linuxservers.io and was checking out their blog last night, some good and relevant articles there, IMO. Seem like pretty cool bunch of dudes. A much smaller (and less slickly marketed) group than I was expecting, to be honest, based on their very outsized awareness / reputation in container circles around the Internet already. Good for them!
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Another article I came across some time ago, which I thought was a pretty good exposition of some of these various technologies and products I keep reading about around (and under) containers, including which companies they came from, along with a bit of history:
You Don’t Have to Use Docker Anymore
That sort of thing is very valuable for someone like me that is new to it all and may not have been following the evolution of it all along as some of you have. I think it's also important to understand what companies are behind which technologies and why, as an important metric before investing any significant amount of my own precious personal resources (time, energy) into learning any more about said technologies (much less using or becoming more "invested" in them).
One of main things I have been picking lanefu brain about is why he like certain tools he does in preference to Docker. I don't think they mention his preferred tools in the above article, however I suspect he may agree with the general gist of it.
Generally speaking, there are several boards meeting your requirements, as "server" use-cases (as opposed to "desktop") have been much better supported for a much longer time now. I used Cubietruck for such tasks for very long time (and still do) however there are better boards available nowadays for actually even less money (read on).
Now to specifics, I used to think SATA was necessary, too, until I read this glowing review of particular USB to SATA adapter by tkaiser (from 2017!). Surprisingly, this device is still available here. I have several of them and they have worked well for me.
If you are willing to consider such adapter (instead of strictly sticking with SATA requirement, which as you noticed is more rare), this of course open up the possibilities a lot. When I needed to buy another little "server" board a year or two ago, I chose ODROID-XU4 at that time which are (like Cubietruck) still 32-bit, however still quite powerful with a lot of CPU and USB3 and RAM, etc. and can be had for ~60 USD these days. Other than the adapter caveat, this meet all your requirements and I think you might be happy with, I know I (and others) have been. I think they went down in price because they are "only 32-bit" however this means (to me) just a good deal to be had (maybe?). To make "apples to apples" comparison, you will need to add the price of PSU, eMMC, SATA adapter, etc. to that figure, though.
And that is where I personally am at, currently.
Now going forward, there are a lot more newer and more interesting boards, especially some of RK3399 (64-bit) based ones as Werner brought up. One of these will probably be my next purchase at some point. They will cost a little more (I think?) but as always, add costs of PSU, flash (eMMC or sdcard), etc. to get the full picture on any price comparison. Some of RK3399 even support fancy stuff like NVMe, etc.
One final generality, I always recommend to stick to Armbian Supported Devices list as a starting point for any research. But you probably know that already. And remember, even some boards that look great "on paper" can have little gotchas, or be better for this use case or that, e.g., N2 have most raw power in CPU but is limited by I/O.
I learned that on some NicoD (YouTube) video, he has made some good ones, maybe you want to check them out. He is focused more on "desktop" usage, but has a lot more experience with a lot more boards than I do, especially some of these newer ones and so I find his videos still very informative.
Let us know your thoughts more and how your research is coming along, if the right person see your post maybe they save you from one particular little problem or another.
