The driven element of a multi-element cubical quad is usually made of wire, and there is no adjust for SWR. How can adjustable SWR be provided for such an antenna ? Can a gamma match be used ?
A gamma match is very common for any loop style antenna (or, indeed, Yagis) for this exact purpose. Note that a fair amount of the math references out there will use a $\lambda$/4 monopole as a reference (probably because the technique was invented for MW Marconi style monopoles).
However, there is lots of practical advice in the usual places, so if you don't want to do that math you can probably just look up reference values. Since you are using wire (and not, for example, tubing) then the matching will be easier; if the elements of the gamma match and the antenna proper are the same size the math is easier as well.