[How do I turn off this initial triangle?]

I was having this problem with a new cr10s pro v2. It was quite annoying. The fix suggested above works, however, and now my gcode from cura works perfectly.

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G28 ;Home
M420 S1 Z2 ;Enable ABL using saved Mesh and Fade Height

To this:

G28 ;Home
G1 Z5 F5000 ; lift nozzle
G29 ;Enable ABL using saved Mesh and Fade Height

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