With 3/4 way circuits, you often don't get a choice
A smart switch typically needs always-hot, switched-hot and neutral all in the same box obviously. That often does not exist in 3-way / 4-way topology.
"Modern home. Every box must have neutral" -- #1 not every box: some 3-way switch locations are exempt. #2 Even if neutral is present, if always-hot is not present it defeats the purpose of having neutral.
Poaching neutral is Right Out. You cannot steal neutral from another cable (and certainly not another circuit). That will cause current imbalance which will cause all manner of practical and regulatory havoc.
The entire 3-way circuit needs to be rethought
When introducing smart switches to a 3/4-way circuit, one must map the circuit and see where it's possible to put the smart switch master. This may require using matching smart-switch remotes if you want full control at your preferred location.