The key letter in UFO is U. Whoever saw it or took a picture of it etc cannot identify it and doesn't know what it is.
That's also why you only see blurry photos, because if the photo was clear it wouldn't be an unidentified object anymore - you would know what it was, it would be something benign and the case would be closed.

If you're going to put a backdoor in something, you'd always want deniability so of course you'd make it look like a bug.

In terms of lowest budget, they don't actually have to develop any firmware at all for a lot of devices. There is already open source firmware like OpenWRT which they could ship. This would both save them money and provide a better experience for users.

Sure it's rare in a datacenter, but i was thinking more of things like laptops which will be moved frequently and possibly subjected to shocks. Something that's in a socket is more likely to work loose.
Also someone deploying servers in a datacenter is more likely to know what they're doing, a random consumer buying a laptop is likely to only consider the price and nothing else.

You mean "they use memory which isn't rate for the clock rate you're applying to it", and yes, that can absolutely happen. It does not "drag the system down". A synchronous DRAM is either stable at a certain clock rate, or it is not. Physically, this comes down to binned silicon.

The memory will be rated for a particular clock, and will usually report that rate via SPD.
Depending on where you put that memory, it may operate the memory at the clock it supports instead of what the system would prefer (thus reduced performance), or might force the memory to run at a higher clock (thus overclocking it and potentially overheating/instability). Some systems will let you adjust memory clocks/timings in the BIOS, some will not.
You also have shady memory vendors where the SPD can be reprogrammed to report a higher clock.

But yes, with replaceable parts you have potentially infinite variables to consider. With fixed parts you take those variables away and have a single known good configuration.

You can run some random binary apps from the 90s on either platform, there are many more which won't work. There are plenty of games designed for win9x which don't work on current versions for instance.
With Linux it's less common because most software is open source and can be recompiled.

There's also two classes of problems that come up with running old binaries:

1) missing userland dependencies - where the binary is dynamically linked and depends on libraries which were present on older systems but are not present on current ones - this is what breaks most older linux binaries as there has been quite a lot of churn over the years. On the other hand it's relatively easy to fix by providing the userland libraries it wants. This happens on both platforms, but is a lot more common on linux because windows still ships with a huge set of old libraries including ones which are very rarely needed.
2) incompatibilities at the system level - where even with all the required libraries, the binary is unable to run. this actually happens more often on windows, linux has been very good at maintaining userland compatibility over the years.

Stability in that with removable memory people could buy all kinds of random stuff - some of which is complete junk.
Stability because the sockets and connectors can become dirty or corroded, the retention clips can become loose or break.
Some brands of memory consume more power then others and generate more heat, so the machine needs to be engineers to be able to cope with that or suffer the stability/longevity consequences.
People also put in incorrectly clocked memory which either doesn't work at all, drags the system down to the speed of the memory causing unexpected performance issues, or overclocks the memory to the rate the system expects resulting in heat and stability issues.
All of the above translates into support headaches. People buy cheap junk memory, or incompatible memory etc.

And yes, power is important these days too - especially on portable devices. Having fixed components also makes the power draw predictable, start inserting random memory modules and the power use could go up, and thus your battery life goes down.

Or an old used laptop which you could probably get for free, and which should still be more than capable of running slackware.

It's a question of arbitrarily destroying perfectly good merchandise, because they would rather destroy it to keep the price artificially inflated, than sell it off cheap and thus decreasing the average price.

No this is saying that if you don't want it, you must offer to sell it to someone else or give it away, you're under no obligation to keep it. And if you've paid waste disposal fees then the waste disposal supplier should have right of resale/donation/recycling as they see fit.

There is misprinted currency, it often commands a higher than face value once someone identifies the misprint.
Silicon wafers are either non functional (so its waste, not discarding a working product) or most partially functional chips are sold as lower spec products (eg faulty cores disabled, lower clockrate etc).
Something like an automobile consists of many thousands of discrete parts, so the individual faulty parts get replaced until you have a functional vehicle again.

In some cases they could also remove the branding, and sell it as cheap unbranded goods somewhere.

There is very little that doesn't support ARM these days.
Pretty much all the open source databases have long been ported to ARM and work just fine. Even things like Oracle have official support for ARM.
ARM is becoming increasingly popular in datacenter use, and RiscV is becoming more widely known too. If you're a developer working on a new project you should absolutely be building architecture agnostic code that can be deployed onto whatever hardware provides the best value.
If you're maintaining legacy code than you should also be considering this.

You're going to have compatibility problems whatever you do. A lot of that binary software might have been compiled for older systems so doesn't work on current ones even if you are using a compatible processor.
These days mobile games are very popular, and most of these are natively compiled for ARM. A mac can run most iOS software, and Linux/ARM can run most Android software.

The mini has an option for 10GB built in, has done for several years now.

People often make the mistake of comparing a macbook pro to the cheapest consumer line from dell or similar. Apple don't have any offerings for the budget laptop market.

If you compare it to the higher end models the macs end up similarly priced or often a bit cheaper for similar spec, and often do a lot better since the M-series came out.

Isn't the minecraft server java based? That should run just fine so long as you're using an ARM JRE.

That's the point most people don't get.
On package memory allows for higher performance, lower cost, lower support headaches and better stability. It makes no sense from a commercial perspective to sacrifice all these points to allow 5% of customers to upgrade the memory later.