Distr is a modern Open Source alternative to Replicated. We have a more in-depth comparison over here https://distr.sh/compare/replicated/. If you have any questions, I’m happy to help.
TL;DR: Octopus Deploy has a strong focus on CD, providing a Cloud based framework to push your software to multiple targets. Distr also supports directly and continuously deploying your software to various deployment targets, but it additionally supports the pull approach, where the customer fully self-manages their infrastructure and simply fetches the application or artifacts from Distr.
Octopus Deploy also offers deep Argo CD integration (after they acquired Codefresh). On the other hand, Distr is completely open source and can be self-hosted if desired.
If you’re interested in specific features, I’m happy to go into more detail.