I reconnect the old bt remote. Here's the output for comparison. It appears as /dev/input/event3, strange the vendorid is 0000 instead of 2717, but it indeed works. Any idea?
LibreELEC:~ # ls -l /dev/input/
total 0
drwxr-xr-x 2 root root 100 Jan 1 2015 by-path
crw-rw---- 1 root input 13, 64 Jan 1 2015 event0
crw-rw---- 1 root input 13, 65 Jan 1 2015 event1
crw-rw---- 1 root input 13, 66 Jan 1 2015 event2
crw-rw---- 1 root input 13, 67 Dec 15 08:32 event3
crw-rw---- 1 root input 13, 63 Jan 1 2015 mice
crw-rw---- 1 root input 13, 32 Jan 19 2018 mouse0
LibreELEC:~ # cat /proc/bus/input/devices
I: Bus=0010 Vendor=0001 Product=0001 Version=0100
N: Name="aml_keypad"
P: Phys=keypad/input0
S: Sysfs=/devices/meson-remote.12/input/input0
U: Uniq=
H: Handlers=kbd mouse0 event0
B: PROP=0
B: EV=f
B: KEY=7fffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff fffffffe
B: REL=103
B: ABS=0
I: Bus=0010 Vendor=0001 Product=0001 Version=0100
N: Name="gpio_keypad"
P: Phys=gpio_keypad/input0
S: Sysfs=/devices/gpio_keypad.46/input/input1
U: Uniq=
H: Handlers=kbd event1
B: PROP=0
B: EV=100003
B: KEY=100000 0 0 0
I: Bus=0010 Vendor=1b8e Product=0cec Version=0001
N: Name="cec_input"
P: Phys=
S: Sysfs=/devices/virtual/input/input2
U: Uniq=
H: Handlers=kbd event2
B: PROP=0
B: EV=3
B: KEY=20000000 0 0 0 0 0 0 0 0 0 0 fc004 4c00 0 0 1 4 10300 51fa 40000801 1e1680 0 100000 10000ffc
I: Bus=0005 Vendor=0000 Product=0000 Version=0000
N: Name="小米蓝牙遥控器"
P: Phys=00:1A:7D
A:71:11
S: Sysfs=/devices/virtual/misc/uhid/0005:0000:0000.0001/input/input4
U: Uniq=F4:B8:5E:A0:F3:58
H: Handlers=kbd event3
B: PROP=0
B: EV=120013
B: KEY=10000 7 ff9f207a c14057ff febeffdf ffefffff ffffffff fffffffe
B: MSC=10
B: LED=1f
bluetoothctl
[XiaoMi RC]# info
Device F4:B8:5E:A0:F3:58
Name: XiaoMi RC
Alias: XiaoMi RC
Appearance: 0x03c0
Paired: yes
Trusted: yes
Blocked: no
Connected: yes
LegacyPairing: no
UUID: Generic Access Profile (00001800-0000-1000-8000-00805f9b34fb)
UUID: Generic Attribute Profile (00001801-0000-1000-8000-00805f9b34fb)
UUID: Immediate Alert (00001802-0000-1000-8000-00805f9b34fb)
UUID: Link Loss (00001803-0000-1000-8000-00805f9b34fb)
UUID: Tx Power (00001804-0000-1000-8000-00805f9b34fb)
UUID: Device Information (0000180a-0000-1000-8000-00805f9b34fb)
UUID: Battery Service (0000180f-0000-1000-8000-00805f9b34fb)
UUID: Human Interface Device (00001812-0000-1000-8000-00805f9b34fb)
UUID: Scan Parameters (00001813-0000-1000-8000-00805f9b34fb)
Modalias: bluetooth:v2717p3200d0110