[DOC] remove mattermost references

CONTRIBUTING.md

@@ -23,24 +23,25 @@ Apache Hop is developed by an open and friendly community. Everybody is cordiall
 ## What do you want to do?
 Contributing to Hop goes beyond writing code for the project. Below, we list different opportunities to help the project:
 
-* To report a problem with Hop, open a Hop's [GitHub Issue](https://github.com/apache/hop/issues), log in if necessary, and click on the "+" in the left side bar (Shortcut "c").
+* To report a problem with Hop, open a Hop's [GitHub Issue](https://github.com/apache/hop/issues), log in if necessary, and click on the `New issue` button at the top of the page.
 Please give detailed information about the problem you encountered and, if possible, add a description that helps to reproduce the problem. For more information go to our [info](https://hop.apache.org/community/contribution-guides/github-guide/) page. 
 * Read the [Code Contribution Guide](https://hop.apache.org/community/contribution-guides/code-contribution-guide/)
 * Help With Code Reviews [Code Review Guide](https://hop.apache.org/community/contribution-guides/code-review-guide/)
 * Help Prepare a Release[Release Review Guide](https://hop.apache.org/community/contribution-guides/release-contribution-guide/)
 * Contribute with Documentation [Documentation Contribution Guide](https://hop.apache.org/community/contribution-guides/documentation-contribution-guide/)
 * Translate Hop [Translation Contribution Guide](https://hop.apache.org/community/contribution-guides/translation-contribution-guide/)
 * Support Hop Users
-  * Join us on our [Mattermost](https://chat.project-hop.org/) server and answer questions
+  * Check out our [GitHub Discussions](https://github.com/apache/hop/discussions) and help someone out
+  * Join us on our Slack more information on how to join [here](https://hop.apache.org/community/tools/)
   * Reply to Hop related questions on Stack Overflow with the hop tag or the Hop forums
   * Check the latest issues in GtiHub Issues for tickets which are actually user questions
 * Improve the Website [Website Contribution Guide](https://hop.apache.org/community/contribution-guides/website-contribution-guide/)
 * Spread the Word about Hop
   * Organize or attend a Hop Meetup
-  * Contribute to the Hop blog (coming soon)
+  * Contribute to the [Hop blog](https://hop.apache.org/blog/)
 
 
-Any other questions? Reach out on the Hop [chat](https://chat.project-hop.org/) to get help.
+Any other questions? Reach out on the Hop [Mailing lists](https://hop.apache.org/community/mailing-list/) to get help.
 
 ## Further Reading
 ### Submit a Contributor License Agreement

README.md

@@ -37,7 +37,7 @@ There are various things you can do to help Hop continue moving forward quickly:
 
 - Log bugs, request features in [GitHub](https://github.com/apache/hop/issues)
 - Ask questions in the [mailing lists](https://hop.apache.org/community/mailing-list/)
-  or [mattermost](https://chat.project-hop.org/hop/channels/dev)
+  or [GitHub Discussions](https://github.com/apache/hop/discussions)
 - Help us write or fix documentation (lot of opportunities)
 - Translate Hop. See our [i18n guide](https://hop.apache.org/dev-manual/latest/internationalisation.html).
 - help fix some [sonar issues](https://sonarcloud.io/dashboard?id=apache_hop)

assemblies/static/src/main/resources/README.txt

@@ -16,7 +16,7 @@
  */
 
 When finding issues please log a bug in GitHub https://github.com/apache/hop/issues
-When you have a question you can use our mailing list (http://hop.apache.org/community/mailing-list/) or Mattermost Chat (https://chat.project-hop.org/hop/channels/dev)
+When you have a question you can use our mailing list (http://hop.apache.org/community/mailing-list/) or GitHub Discussions (https://github.com/apache/hop/discussions)
 
 
 Installation Instruction:

docs/hop-tech-manual/modules/ROOT/pages/hop-vs-kettle/if-you-know-kettle.adoc

@@ -25,7 +25,7 @@ under the License.
 
 Hop wants to allow data engineers to be able to deliver high quality work, deliver that work fast and integrated with bleeding edge technology.
 
-We want Hop to be completely open source, and are eager to hear your feedback on our https://chat.project-hop.org[chat] and just as eager to see your bug tickets and feature request in https://github.com/apache/hop/issues[Github Issues].
+We want Hop to be completely open source, and are eager to hear your feedback on our https://github.com/apache/hop/discussions[Github Discussions] and just as eager to see your bug tickets and feature request in https://github.com/apache/hop/issues[Github Issues].
 
 As an open source first project, we started the https://www.apache.org/[Apache Software Foundation] https://incubator.apache.org/[incubation] process in September 2020 and graduated as and ASF https://projects.apache.org/[top level project] in December 2021.