Comment 8 for bug 1758023

Same problem.
Change acceleration in mouse settings have no effects.
My keyboard and mouse appears in double (see image).

$ xinput
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ ARESON Wireless Mouse id=13 [slave pointer (2)]
⎜ ↳ ARESON Wireless Mouse id=14 [slave pointer (2)]
⎜ ↳ RAPOO Rapoo 2.4G Wireless Device id=11 [slave pointer (2)]
⎜ ↳ RAPOO Rapoo 2.4G Wireless Device id=10 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
    ↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
    ↳ Power Button id=6 [slave keyboard (3)]
    ↳ Video Bus id=7 [slave keyboard (3)]
    ↳ Power Button id=8 [slave keyboard (3)]
    ↳ Sleep Button id=9 [slave keyboard (3)]
    ↳ RAPOO Rapoo 2.4G Wireless Device id=12 [slave keyboard (3)]
    ↳ Dell WMI hotkeys id=15 [slave keyboard (3)]
    ↳ Dell AIO WMI hotkeys id=16 [slave keyboard (3)]
    ↳ RAPOO Rapoo 2.4G Wireless Device id=17 [slave keyboard (3)]
    ↳ ARESON Wireless Mouse id=18 [slave keyboard (3)]

Unable to change value above 1 :

$ xinput set-prop 13 "libinput Accel Speed" 5
X Error of failed request: BadValue (integer parameter out of range for operation)
  Major opcode of failed request: 131 (XInputExtension)
  Minor opcode of failed request: 57 ()
  Value in failed request: 0x11f
  Serial number of failed request: 20
  Current serial number in output stream: 21

This is very troublesome.

If you want i am on call to give more information or diagnoses