Hi Mark,
For long term trends it is advised to use the log scale. So with long term trendlines.
A trendline drawn in a log scale is irrelevant in an arithmetic scale and vice-versa. So the trendlines should be displayed only for the type of scale they have been drawn.
And, just for the fun, a nice trendline in log scale on the Apple chart.
https://i.ibb.co/3zGRXZk/20240420-sam-10h31-01.png
The same trendline cannot be drawn in the arithmetic scale
https://i.ibb.co/W5g6GgQ/20240420-sam-10h31-02.png