As we've announced before the new iteration of Newsletter Studio will run on both Umbraco 8 and Umbraco 9. We're in the process of migrating parts of the package to .NET 5 and we've come a long way.
We have an RC (Release Candidate) out that has the same features and core-API as the Umbraco 8-version.
The RC is out in the wild and you're most welcome to try it out. Since Umbraco 9 only support package installation via NuGet you need to install the package this way.
We've made the package available on NuGet, at the moment when the package is in RC one needs to enable "Prerelease" packages to see it.
Install-Package NewsletterStudio -Version 4.0.0-rc2 -PreRelease
https://www.nuget.org/packages/NewsletterStudio/
Once you've installed the package, take some time to look at the documentation.
The Umbraco 9-version is built on the same code and Core as the stable Umbraco 8-version so at the moment there are no known issues.
Please feel free to reach out with questions and feedback to info@newsletterstudio.org.
4.0.0-rc2 - Released 2021-12-02
Solves some critical issues related to dependency lifetimes.
Bugs
4.0.0-rc1 - Released 2021-11-07
We're releasing the first RC for Umbraco 9!
This version has the same features as version 3.0.0.
Install via NuGet and don't forget to check "Include Prerelease" to see the v4-version in the list.