Send Mail Message Body of Invisible Text

Questions & Suggestions
#1

I'm trying to use KM to send an Apple Mail message for the first time, but the body comes out as invisible text. What do I need to do to fix this?

You can see the action, the Mail message, and part of how the sent email looks in GMail in the below screenshots.

Screen Shot 2020-09-22 at 18.54.05
Screen Shot 2020-09-22 at 18.54.051378×1316 128 KB

Screen Shot 2020-09-22 at 18.55.46
Screen Shot 2020-09-22 at 18.55.461896×1902 333 KB

Screen Shot 2020-09-22 at 18.53.01
Screen Shot 2020-09-22 at 18.53.01934×520 21 KB

#2

I haven't found a solution, but I did find a workaround for this.

In Mail's Preferences, on the Viewing pane, disable Use Dark Backgrounds for Messages allows/enables black text.

FWIW, I also tried setting the Message Format (on Composing pane) to Plain Text, but it seems KM-generated emails always come in as RTF regardless of that setting.