Posting the response from the Royal team:
"We are not able to implement support for VMware's free Hypervisor, because VMware restricts certain API actions - we're not making this limitation, and we're also not able to bypass this. Such limitations also apply to well-known backup solutions like Veeam. There's unfortunately nothing we can do against. To be more specific: When running with a free ESXi license the API is only read-only and therefor it is not possible to request the required Remote Console API Tokens to establish a console connection and such stuff. Read more about here: https://serverfault.com/questions/884743/free-esxi-6-5-and-api-support"
This is fine. ESXi 6.7+ come with a new HTML5 web interface anyway that is way better than the standalone client.
VMware ESXi is now supported, but TSX only can list VMs deployed on the free VMware Hypervisor and show their status (on/off). It can't control them or apply any changes.
Basic controls (start/suspend/shutdown) of those VMs would be great.