Such as actual gods being seen doing godly things as a matter of routine.
Basically the same things that make people confident in the existence of real things in the real world. I know my dining table exists, because my spaghetti doesn't land in my lap.
I know gods don't exist, because theists have to eat off their knees.
But what would be godly verses just highly advanced?
"Actual god" versus "just highly advanced" = semantic issue.
A "God" is merely a being or power that's super-duper impressive to those who want to worship him/her/it. Call the conjectured power or being "advanced" instead if you like, but if the worshiper calls it "God" then that's how... and is the one and only way... to determine that it's a deity. It has to be someone's deity to be a deity.
So, could the OP's scenario convince me it's God? If I valued the noise 'gawd' as an explanation for anything, then Yes. But I don't, so No.
"Is it a deity?" is not a problem you can solve like an engineering issue (what is it? what's it made of? how does it work?). Instead it's a question of values. Do you value the word "God" as meaningful? Do "sentient" and "very powerful" and "incorporeal" and "deserves worship" seem like they all fit together in your mind? If not... if the values aren't all there
(maybe especially if the "deserves worship" bit is missing)... then probably "advanced alien being" is what your more science-informed sensibilities are going to make of a powerful incorporeal being that can make you believe it exists.
Yup, sycophancy isn't part of my makeup, so even if some religious sect did present me with their god, and it was able to do all kinds of inexplicable things, and it knew everything, and it was kind and caring, and etc. etc., I still wouldn't worship it.
I might respect it (if it earned my respect, for example by alleviating human suffering); I might learn from it, if it could teach me something plausible and interesting. But worship? Worship is for tyrants. It's a human mechanism for building the ego of a leader, while reducing the risk of rebellion from his minions.
A god worthy of the name would neither want nor demand worship - and a god that's not worshipful is no god at all.
I know that most people are in awe of powerful and/or famous people. But kings, rock stars, CEOs etc. do nothing for me. I don't care if you own the company, or if you are the janitor - the respect you get will depend on what you do and say, not what titles you hold. If you can sack me on a whim, I
might fear you; But if you would do so, just because you can, I wouldn't want to work for you anyway. And fear isn't respect - a mistake that is common amongst gangsters and theists is to conflate the two.
If a being can damn me to eternal suffering, it won't get respect from me as a result - and indeed it would instantly lose any respect I had for it if it damned anyone (including me). Fear? Perhaps. But not worship, nor respect.
The very foundational principle of most religions - that a god can
command respect - is deeply wrong.
Fear god? Sure, if you show me a scary one. Worship god? Why?