StackOverflow
Questions regarding the software can be asked on Stack Overflow, where you can use the mlr3 tag.
GitHub
For bug reports, suggestions, or feature requests please raise an issue in the corresponding GitHub repository. Your issue will be addressed sooner if you provide a reproducible example - e.g. using the reprex R package - and if you open it in the correct repository.
Mattermost
You can join our public Mattermost channel.