Does a free alternative to Proxifier or ProxyCap exist?
Try proximac.
https://github.com/csujedihy/proximac
Proximac is an command-line open-source alternative to Proxifier. With Proximac, it can force App to use SOCKS5 proxy. In the other words, it can forward any App's traffic to a specified SOCKS5 proxy. Moreover, Proximac now can forward all network traffic in your system to a proxy which means you may not need a VPN to do this job. I hope more developers can join this project.