There is an updated pull request by classabbyamp against master on the void-packages repository

https://github.com/classabbyamp/void-packages mininet-2.3.0
https://github.com/void-linux/void-packages/pull/35747

mininet: update to 2.3.0, move to python 3, adopt.
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A patch file from https://github.com/void-linux/void-packages/pull/35747.patch is attached