I have three Sunba PTZ cameras on my network. They're ONVIF compliant, but commanding them in PTZ has required a Windows 10 computer, IE and the vendor's proprietary DirectX plugin.
I run mostly Linux at home. Happytime ONVIF client was recommended to me as a PTZ client. It works in Windows, and also under Wine in Linux, but I've found its PTZ control to be 'glitchy'. (Maybe I haven't found the correct configuration yet).
I stumbled on Shinobi yesterday. It's actively maintained and understands a wide range of network protocols related to video. It runs as a service on Mac, Windows or Linux, understands ONVIF and can control PTZ cameras (although I'd characterize its PTZ control as 'touchy' so far).
It isn't resource-heavy, but neither is it a lightweight. It bogged down on an Atom-based computer I had, but runs fine on a core i5-based PC.
Here's a screenshot of it viewing 5 video streams (consuming 4-5 Megabits/second of mesh network bandwidth):
Orv W6BI
Joe AE6XE