sometimes we don’t even recognize human technology when some random debris washes up on the shore of a beach

It's all for ritual purposes.

I watched a presentation a long time ago that went through the math of Von Neumann probes. I don’t remember the details, but it was something like a sufficiently advanced and motivated civilization could convert a Mercury like planet into enough Von Neumann probes to put one in every star system in the universe in some finite number of millions of years. The argument was something like at this point, there should be one in our solar system. And if there isn’t, why not?

I think Avi Loeb has cried alien too often and too easily to be taken seriously at this point. I think there is about zero chance any of the UAP things are anything. But I wouldn’t be too surprised if there is an ancient probe just dormant somewhere in the solar system. Would we recognize it if we saw it? Maybe not unless we got close to it. Could we find candidate objects that look out of place? Fascinating line of thinking.

Morality and efficacy. It would be really rude and irresponsible to send metal crap all over the universe. It may also be really bad for Earth if we eat all of Mercury. Figuring out the question of "how much mass from Mercury can we send somewhere else before something becomes a problem for life on Earth" sounds like playing with fire.

What if Von Neumann probes kill life on another planet? What if other sentient life meets one and gets offended? Can we even get useful data from a Von Neumann probe that would offset the potential cost of it harming another planet? I don't think it's worthwile or ethical to send such a device into space no matter what is out there.

I don't see the merit in any presentations speculating on alien technology. I can infinitely move the goalpost of how "advanced" my hypothetical alien species are, and thus I can justify virtually any kind of speculative technology they'd be capable of producing.

No we wouldn't

Imagine that you would give a gentleman from mid 19th century discharged tablet. Would he be able to understand what is the purpose of the device? Very unlikely. And that's difference of just 150 years.

If aliens aren't on our tech level +-50 years, but are i.e. 1000 years ahead of us then they would look like wizards and gods to us. If they would be 10000+ years ahead of us, we would be looking on them like animals are looking on us - completely unable to understand what is going on.

easy, peasy. Extraterrestrial technology is:

Any structure that 1) adopts a shape that we can't explain as physics+time (physics being: geological processes, results of forces like electricity, gravity, etc);

2) does not follow our body plan

3) is found out of the earth and

4) is not from us.

Is not in the known list of extraterrestrial objects made for us.

We need also to recognize that there are two types of technology in the planet earth. Human and non-human technology. Is widely accepted that some species other than Homo sapiens developed technology. Many of this animals are in the family hominidae but a beehive for example could be accepted as bee technology. It has a well defined purpose, implies several examples of material design and manipulation. what bees evolved to keep warm in winter is not much different than ours wood cabins, pantries and bonfires. The acari that is riding a honeybee to move far than its range is not too different than us learning how to ride a horse for the same purpose. We adopted and replicated a lot of animal technology like paper, but not all. We still don't dominate the technology to make a clam shell from scratch for example.

Identifying extraterrestrial technology in the planet could be much more difficult because we need also to be able to separate it from non human technology. That technology could be much more subtle than the festival of ligths and steel that we see in the films. Until data most if not all of the "extraterrestrial" signs were found to have a perfectly normal terrestrial explanation.

To me, and the clear answer given by other commenters to this question (thank you all for the succinct answer) are the reason why the current government finger pointing from Dr Kirkpatrick at AARO, the testimony from Grusch this last week, and the lack of willingness from other government officials to acknowledge the known evidence and it's inherit difficulties is alarming. It leaves for more speculation, opaqueness, and indirectly lends credit to the claims of a misinformation and disinformation campaign made under oath by Mr Grusch. People just want clarity, not contradiction. American citizens, including veterans from fifty years ago, are still being treated like morons and charletons. This could stop if the IC and civilian agencies just were honest and did what congress asked them to do, and yet they refuse. Call your representative, call your embassy in the US, and voice your concerns please. I'm tired of seeing senior citizen veterans who have scary accounts from the cold war be treated like whackos.