Text area with Plain text processing doesn't display line breaks

Description of the bug

When using a multiline (text area) field with plain text processing, it is expected that line breaks will apply to the rendered page, but they don't. Drupal 8/9 inserts <br /> tags.

Steps To Reproduce

1. Add a field with a "Text (long)" field type and "Text area (multiple rows)" widget.
2. Set the Text processing to "Plain text"
3. Create content using the new field with multiple lines of text.

Actual behavior

The field is rendered without line breaks.

Expected behavior

The line breaks should be applied to the rendered page.

Additional information

Add any other information that could help, such as: - Backdrop CMS version: 1.21.2