Starting in 2020, I will increase the required Joomla! and PHP versions for all newly released free and paid extensions.
Joomla! Core Version >= 3.9.0 (latest 3.9.x version recommended) PHP Version >= 7.3 (recommended >= 7.4)
Don't worry! You cannot break your site if the requirements are not met and you trigger the installation/update process. All packages will do a pre-installation check, and the installation will be stopped if the versions are too low.
If you cannot update Joomla! or/and PHP for any reason, then please stay with the already installed instances or use an older version that I released before 2020. Though I would strongly advise you using the latest versions for performance and security reasons anyway!