Oh, come on!
It’s obviously a support of some type.
Pool plumbing is not made of metal - it’s PVC. And, this pipe is thin-walled, so it’s probably not even re-purposed iron water pipe.
There are no flanges or threads to make a connection, so it’s not for plumbing, it’s too big for electrical conduit, so ergo, it must be a base for a net or umbrella or something.
I think you’re absolutely right in that it’s a stand for something, probably a satellite like someone (op?) said.
But homeowners, especially unknown previous homeowners hack together odd stuff. Hate to go rooting around in there with a metal rod or just rip it out only to find out the last guy buried an extension under the gravel and brought it up right there for something.
Sounds stupid and it’s probably not the case, but why not just grab a flashlight and check?
Doing something because it’s obvious is a good way to find out the last guy didn’t.
PS, why would you rule that out as being too big to be electrical conduit? You can go to Home Depot and buy it from 1/2" inch up to 2" I think.
Because big conduit is expensive, and only needed for small-gauge wires, which would have no purpose out in the yard. Sure, the pipe itself could be made from conduit, but it seems exceedingly unlikely that it is actually designed to carry huge-current cables.
Weird, it’s exactly the same colour as the support post for my patio umbrella and all the rest of the metal for a patio deck set - table, chairs, umbrella The umbrella central post - same colour - drops into a pipe like that, except my umbrella stand ends in a heavy metal wide base. probably the same moderately thin metal - too thin for a pipe that holds pressure, nicely finished. I think it’s for a second umbrella.
I figured it was spray painted to match the surroundings. If it is for an umbrella, the base could simply be buried a few inches down. The only reason I like the satellite idea more is because that seems like an odd place for an umbrella, but it could still be an umbrella stand.