[steps up on soap box]
The X-Y Axis / Row-Column Grouping in Report Charts "break" in the Lightning Home Tab and in Embedded Report Charts on Lightning Pages. This has been a nagging issue since [checks notes] "Forever".
Currently if you create a Matrix Report and Chart with the Report Columns displayed on the Chart X-Axis (the way everyone likes to see it) and then you add the Report Chart to a Lightning Page, the chart "breaks" and displays the ROW Groups on the Chart X-Axis. The only "solution" is to change the Report so that the Chart X-Axis are ROW Croups, which is... [checks notes] the way nobody likes to see it.
Is fixing this problem anywhere on the Road Map?
And before anyone says "IdeaExchange" this is a FLAT-OUT BUG, and bugs should not need to go through the IdeaExchange and be upvoted (they should be fixed).