Another proxmox-esque project I've been watching is Sylve, a control plane for FreeBSD that provides a web interface to jails, bhyve VMs, and containers [1]. It's new-ish, but it looks like a possible sweet spot replacement for both proxmox and TrueNAS (which was originally also built on FreeBSD before they switched to Linux IIRC), at least for my homelab-ing use case. Potentially eventually for environments at greater scale also. The company behind it is a software consultancy and Sylve is built with their actual business needs in mind, and is BSD-licensed like the OS it runs atop.

One of the developers building Sylve gave a talk last year [2].

[1]: https://sylve.io/

[2]: https://youtu.be/wo4oD5UON30