Advocate IHi - the community threads point at the Microsoft "Power KPI" custom visual as a possible solution. However, this visual doesn't have the same features as the standard line chart, eg: it doesn't have the axis zoom features as reported in this reply (and I've confirmed myself) so I can't use it:
https://community.fabric.microsoft.com/t5/Desktop/discrete-graph-step-chart/m-p/1850954#M714909
At the moment the standard line chart visual implements a very strange step algorithm where the step is always halway between two data points. For example, if you have 4 data points at the start of 1900, 1902, 1904, and 2004, then the step will occur at 1901, 1903, and ... 1954 ?! The graph seems to suggest your data changed in 1954 instead of 2004.
This is so strange, that I think the stepped interpolation algorithm for the standard line chart is broken, or the visual should at least offer "step-after" as well as the current step algorithm.
Hope that helps? (love power BI, hope we can continue to make it better 🙂 )