I think there can be different vintages.

’70s vintage is different than ’90s vintage, but there are gems from both eras.

Anything that ain’t got any AI in it, nor requires an account to function, or if it was made by a hipster Silicon Valley startup with a horn-rimmed glasses and flannel wearing spokesman it must be at least old enough for that company to have since gone out of business?

I think this is highly variable depending on the object in question. Whatever the “current era” is for, say, cell phones is sure to be a lot different than the one for A/V equipment, or computer hardware, or cameras.

Like, CED and LaserDisc are surely vintage by now, right? So what about HD-DVD? It’s not that old, objectively, but it unquestionably lost its format war and thus has already been buried by history.

Anything older then you are.

I would say at minimum it has to be something no longer commercially available, or if it is something which has been sold continuously for a long time, the “vintage” one may have some difference to the current revision. If I can go to the store or online and buy one brand new, I would say that it isn’t vintage.

I do not think that there is a flat age which could apply to all categories of electronics. For a smart phone or a gaming PC, something from the 2010s might be “vintage,” but for audio gear or other things, the bar for something to be “vintage” might be significantly older.

Edit: thinking about it more, perhaps a good definition might be something which is significantly different in some way to comparable items being sold today. If there is no difference in how it looks or functions to something new, then it’s just old, not vintage, but if there is some aspect of it which has since changed over the years, maybe that qualifies it as vintage.