Logarithmic Scale Base

To my knowledge, there is not a built in way to use a non-integer base for the built in logarithmic axis.

The "trick" I would use would be to plot the desired logarithms (=LOG(number,1.2)), then use a technique like this to fake my own logarithmic axis:
The technique being used to create a reciprocal horizontal axis: https://peltiertech.com/reciprocal-chart-axis-scale/
The technique being used on a base 10 log axis to get different text for the axis labels: https://peltiertech.com/Excel/Charts...cNotation.html