Sendy is a self-hosted application for email newsletters. You install it on your own web server (PHP with MySQL or MariaDB) and send campaigns through Amazon SES; according to the website it also works with SendGrid, Mailjet and Elastic Email. There is an optional AI assistant. The licence is a one-time purchase that covers one domain, with free updates within a major version. The vendor also offers an installation service.
Because you install Sendy yourself, your subscriber lists and campaign data sit in your own database, on the hosting you choose, for example in the EU. Sending goes through Amazon Web Services, a US provider, for which you set up IAM credentials and SES and SNS connections yourself. Whether that meets your requirements therefore depends on the sending provider you choose. The website does not say which company develops Sendy or where it is based. Sendy is commercial software, not open source.