Thanks for your suggestions. I’ve tried everything - latency settings, screen refresh rate limit, frame capping at 30 and 60FPS, LOD down to the lowest setting, DX11/12, antialiasing OFF/TA/DLSS. Allowing the CPU and GPU plenty of headroom still cannot result in smooth frametimes.
I’m assuming those of you who have the frametime graph displayed will see the same not-quite-smooth line.