SUMIF function - Office Support only says:
criteria Required. The criteria in the form of a number, expression, a cell reference, text, or a function that defines which cells will be added. For example, criteria can be expressed as 32, ">32", B5, "32", "apples", or TODAY().
Which gives absolutely no clue about what are and aren't possible inputs and what their syntax and semantics would be. (E.g. if it's a function or expression, how do I mark the point where the cell's value should be inserted?)
3rd-party sites, e.g. https://exceljet.net/excel-functions/excel-sumif-function and https://www.myonlinetraininghub.com/excel-wildcards-in-your-sumif-countif-and-vlookup, give some examples of possible inputs -- which apparently include wildcards (with nonstandard markup to boot) that the doc says nothing about whatsoever. But they cannot guarantee that their list is complete, nor which Excel version(s) each item is applicable to.
Is any more conclusive documentation available?
Clarification: I'm asking specifically about official sources (only they can be called "documentation", but apparently this was unclear). I need to be sure that I have complete and accurate information, and no 3rd-party resource can guarantee that (unless it's a result of reverse engineering the corresponding Excel functionality or something).
E.g. I suspect that this "criterion" functionality is common for several Excel functions, and there's some dedicated article on it that I could easily find if only I knew the keywords to look for (nothing of the kind is found by "criteria").