The phrase "without passcode" usually hides one of two very different situations, so start by identifying which one you are in.
You know the device passcode but not the Screen Time passcode. Go to Settings > Screen Time > Change Screen Time Passcode > Forgot Passcode? and authenticate with the Apple Account that set it. On iOS 17+ this resets the Screen Time passcode only. If you are the Family Sharing organizer and the passcode is on a child's device, do the same from your own phone under Settings > Screen Time > [child] — no passcode from the child's device is required.
You do not know the device passcode either. Then nothing short of a restore will help, and a restore erases the phone. Recovery mode plus Finder/Apple Devices, or Apple Support with proof of purchase. Activation Lock still applies afterwards.
The trap to avoid. Sites advertising a "Screen Time removal tool" that works "with no data loss" are almost always either (a) a paid wrapper around the Apple Account reset above, or (b) a configuration-profile trick that installs an unsigned profile on the device — which is a security hole, not a fix, and it breaks on the next iOS update. If the device is a school-issued or MDM-managed phone, removing the profile is also a policy violation that can brick the enrollment.
Once you are back in, the durable fix is structural: keep the Screen Time passcode on the parent's Apple Account, keep the child's device in the family group, and write the passcode down somewhere you control. Families that also run Android or a family PC usually keep those under one dashboard instead of stacking four separate apps — Ultimate Phone Spy handles the Android, Windows and Mac side (parental control features), while the iPhone stays on Apple's native controls because iOS does not permit deeper access.