Hi and welcome at the new community portal,
quoting there from the last announcement related to the closing of the ML:
this is a reminder:
Only 9 days to go until this mailing list is shut down.
The community forum is already very active.
Lets meet there! :
so you already have found the new home of discussions around VT development. 
Just to summarize:
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OpenVAS - Open Vulnerability Assessment Scanner is deprecated and probably will be removed soon. New content will be maintained in VT Development - Vulnerability Tests - Greenbone Community Forum and probably split into separate topics at some point in the future.
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If you have plugin/VT specific questions related to development, VT requests or false positive/false negative reports you can use the following category: Vulnerability Tests - Greenbone Community Forum
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If you have issues with the Feed (e.g. slow sync, no sync at all or similar) you can use the following category: https://community.greenbone.net/c/feed-services
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And finally when having question on how plugins/VTs are used (e.g. how the scanner is starting them) you can use the following category: https://community.greenbone.net/c/gse
Hope this gives a brief overview over the new communication channel here.