Amplenote is an app for notes and tasks. Notes can be linked to one another, tasks and a calendar are integrated, and the functionality can be extended with plugins. According to the help centre there are also Vault Notes, a form of protected notes, and an explanation of how notes and uploads are secured. The service runs as a cloud service with web and mobile apps, and it is a closed product that is not open source.
Amplenote is built by Alloy.dev, the parent company that also makes GitClear; according to Amplenote's blog, Alloy is based in Seattle. It is therefore a US vendor. The help centre contains an article on a data processing agreement that refers to the GDPR, but the vendor's documentation does not say where data is hosted. No self-hosting option is described. For a European organisation, what matters most is that notes and tasks sit with a US provider, which is part of assessing exposure to legislation such as the CLOUD Act.