There is a new pull request by travankor against master on the void-packages repository

https://github.com/travankor/void-packages openvpn
https://github.com/void-linux/void-packages/pull/23429

openvpn: add mbedtls build option.
Default to it since openvpn is broken with libressl-3.1.X.

A patch file from https://github.com/void-linux/void-packages/pull/23429.patch is attached