How can I disable auto-capitalization in Notes?

Hello sy.ableman,

Thank you for reaching out to Apple Support Communities.

We were able to find these formatting options for Notes:

"Format text

You can apply a style—such as heading or body—to quickly format a paragraph.

Note: To use paragraph styles, you must be using upgraded iCloud notes or notes stored on your Mac.

1. In the Notes app  on your Mac, click a note in the notes list or double-click a note in gallery view.
2. To format text, do any of the following:

• Change the formatting of selected text (such as changing a phrase to bold): Select some text, click the Format button , then choose an option (or use the Touch Bar).
• Change text alignment: Click anywhere in the text you want to change, choose Format > Text, then choose an option.
• Change text font, color, size, and more: Select the text you want to change, Control-click the selection, choose Font > Show Fonts, then use the Fonts window to make changes.
• Apply a paragraph style to a paragraph: Click anywhere in the text you want to format, click the Format button , then choose a style.
• Change the default title paragraph style: Choose Notes > Preferences, click the “New notes start with” pop-up menu, then choose an option."

More details can be found here: Write and format notes on Mac

Can you provide a few more details? Does this only happen within the Notes app? Also, what is your exact macOS version?

Cheers!