When a form is submitted inside Landing Page in frontend it will be submitted twice. Submitting form directly from the Form Content works as expected.

Steps to reproduce
1. Clean installation of 2.4.2
2. Create a new form with only two fields: Single Line and Button. Leave all settings to default.
3. Add newly created form to Home Landing Page.
4. Go to Home Landing Page in frontend, submit the form.

Result
There will be two submissions for Form in Submissions tab inside BO.