https://www.chartjs.org/docs/latest/axes/styling.html refers to:
Namespace: options.scales[scaleId].grid("scaleId" doesn't seem to be defined, am assuming it is x or y)
Have tried different permutations
Chart.options.scales = { x: { grid: { ... }} // TypeError: Cannot set property 'scales' of undefined
Chart.defaults.scales = {x: { grid: { ... }} // no complaints but no joy either
yet passing the above as parameters to each new Chart() constructor then it works ok