Official tool? Oh, you mean some UPNP thingy that spews all over the network in an attempt to protect the end-users from having to think? Some people are allergic to that, y'know. I'm sorta middle of the road myself, it sure is handy sometimes, but I'm not the biggest fan. See https://nordvpn.com/blog/what-is-upnp/ for the tale of a non-fan.
Of course, there are other tools out there:
IPAM - properly record the layout of your network and all IP addresses in the first place
Wiki - generally document everything
network scanner (nmap or other) - for finding the devices that have snuck onto your network without being documented or those that have gone rogue
As for Proxmox Virtual Environment (PVE), though it is very popular in the self-hosted world, given the dual-licensing and the usability on a insanely wide range of hardware, Proxmox positions it as an enterprise product, and us enterprise network folks aren't much for UPNP.
It's all over the map depending on the product line. As Engineers-rock pointed out, there are product lines that allow one switch wired into the circuit and everything else has to be battery-powered remotes. (Which in the case of Lutron Caseta look almost exactly like their switches and can be mounted on a wall behind a switchplate.) One nice feature is that you can directly pair the remote with a switch, so it works even if your hub is offline, assuming the remote and switch are close enough to each other to communicate directly.
Another product line you might want to look into is the Jasco/GE Embrighten switches. They make "Add-on" switches that work with their smart switches that can be wired in a box with neutral and 2 travellers coming in from the smart switch's box. If you look at the wiring diagram (https://byjasco.com/media/manuals/46200-QSG-v1.pdf) you'll realize that the add-on switch is not actually switching anything, but is acting as a remote for the smart switch, while being powered by the smart switch.
There are other switches, an example, I believe, are the Aqara switches, where you're expected to integrate the switch and button of your choice with a hub and the whole affair is the lowest common denominator "have something happen; have hub tell switch to switch" that should work with any smart switch.
For the sake of completeness, I'll mention that many (most?) smart switches will work with the existing 3-way switches so long as you put the smart switch nearest the breaker (so it always gets power on the terminal it expects to). See https://help.inovelli.com/en/articles/8269832-red-series-dimmer-switch-wiring-schematics for Inovelli's instructions for doing that with their Red Series devices, as an example. The user experience may vary, however.