the vm & container network space is a mess.

slirp/slirp4net is not worked on for a while. I think all the effort now goes to the worse name project in history: pasta.

ESXi has great virtual switch support, more extensible, adaptable, and scriptable than Hyper-V so far as I’ve seen.

I'd also recommend KVM/Libvirt and OpenVSwitch. Especially it combined with Netplan it becomes trivial to set up and use.

OVS seems great but it doesn't seem to garner much hype these days. Does it carry too much connotations from OpenStack, or why isn't it the defacto solution for all L2 bridging/virtual networking for containers/VMs/routers/etc?

Most people just need data to come out the NICs on certain tags. If you need L2 between guests (in a way you can't just do that from the network in the first place) you can either just do it in container or on the host without having to set up an entire virtual switch. The configuration manages fine outside an OpenStack environment it's just a ton of work for very little squeeze.

Same for the virtual VMware switches on Workstation. I'd love to have a way to connect "something" to a VM that is running in VMware Workstation.

There was once a "VMware Virtual Network SDK" or something, but I couldn't find anything that made any use of that (and now with VMware being part of Broadcom I think it's getting more and more impossible)

There are 3 APIs for HyperV that I know of... you are probably going to use the Host Compute Network section, for instance.

https://learn.microsoft.com/en-us/windows-server/networking/...