UR website[0] seems to suggest +- 10N (a kilo resting on your neck) with their stock implementation. I imagine you're going to want something better than that.
What Force/Torque sensor do you use? Some of them are temperature sensitive and require a good warm-up period before they can be used to achieve good performance.
Not OP but I've written custom force control code for a UR5e. There's a six axis force sensor on the end effector for the e model which has a pretty noisy raw output. After some filtering we were able to get a pretty sensitive controller. I didn't measure it, but far less than 10N.
What Force/Torque sensor do you use? Some of them are temperature sensitive and require a good warm-up period before they can be used to achieve good performance.
[0]https://www.universal-robots.com/how-tos-and-faqs/how-to/ur-...