Decades ago, Return and Enter were two different keys for that reason: Return to insert a line break, Enter to submit your input.

Given the reduction to a single key, the traditional GUI rule is that Enter in a multiline/multi-paragraph input doesn’t submit like it does in other contexts, but inserts a line break (or paragraph break), while Ctrl+Enter submits.

Chat apps, where single-paragraph content is the typical case, tend to reverse this. Good apps make this configurable.

Before that, page-mode terminals used <Return> to move to first field on a subsequent line (like a line-based <Tab>) and sent the page only on <Enter> or <Fn-key>. This made for quick navigation w/ zero ambiguity.

don't get me started on backspace vs delete...

Carriage return and line feed go way back. Tty stands for teletype. A computer was the job description of a person.

It’s turtles all the way down.