erellsworth

Just use Contact Form 7’s normal shortcodes like so:
‘[email* your-email]’ 
‘[checkbox sendinblue-opt-in default:1 “Subscribe” ]’ 
‘[hidden sendinblue-list-id “13”]’
That’s all there is to it.

Contact Form 7 SendInBlue Opt-in Checkbox

Not working

It integrates the form with Send In Blue very well. =)

but if we are using the official SendinBlue plugin, they seem to conflict and the officil plugin stops working.

It is a very useful plugin.

WordPress plugin to add a SendinBlue Opt-in checkbox for Contact Form 7

Webtica

A lightweight but feature packed Sendinblue / Brevo integration for Elementor forms. 
With this integration you can send your form data and contacts to Sendinblue / Brevo as easily as the standard integrations. 
Keeping performance in mind this integration doesn’t add any additional scripts on page load. 
Feel free to post any feature requests and possible issues.

Integration for Elementor forms – Sendinblue

Connect your Elementor Pro forms to Sendinblue/Brevo to easily capture and manage contacts from your website.

Contact Form 7 SendInBlue Opt-in Checkbox vs Integration for Elementor forms – Sendinblue