Jetpack Retrocompability for older WP Versions

The problem I’m experiencing is that Jetpack stopped to work in my site. Trying to find out the reason I realise that Jetpack no longer supports WordPress 4.9 or older. So the older sites I’ve implemented have to update to 5.x to continue use Jetpack, is that so?

There’s no legacy version of Jetpack? I would like to install Jetback in order to keep the sites that are in sites with WP in version 4.9 or older. Thanks!