If you are not already using Confluence, these are the options:
The easiest way to get started is the free version of the cloud proposition. While it offers the same features, it lacks the possibility to define permissions on space level. This means that users have either no, or admin access to the spaces. There is no read-only option.
If you will use Confluence only for Instant 27001, this might be acceptable. And it is always possible to upgrade to the paid version later.
Confluence cloud is hosted with Amazon Web Services, but unfortunately it is not possible to select the geographic location of your data. Atlassian does however comply to GDPR regulations.
The paid version of the cloud proposition offers additional support and the option to set detailed permissions on a space level. You will be billed monthly based on the amount of active users, at $5 per month.
You can always move the content to your own server instance later.
If you really don’t want to rely on cloud services, or want to have absolute control over your data, you can also opt for the server version. This will be a one time fee of $10 for up to 10 users.
On October 16, 2020, Atlassian has announced the discontinuation of the Server products per 2021, so this may not be future-proof.