Unfortunately, Logitech MX Master and MX Keys might not always be discoverable even in pairing mode.
The simplest way is to purchace Logi Bolt receiver and use it to pair mouse.
- solaar
Add current user to udevadm group:
sudo groupadd udevadm # Skip this step if udevadm group already exists
sudo usermod -aG udevadm $USERGrant permissions to access /dev/uinput by udevadm group.
To do that, create /etc//udev/rules.d/99-uinput.rules:
SUBSYSTEM=="misc", KERNEL=="uinput", GROUP="plugdev", MODE="0660"
Reload udev rules:
sudo udevadm control --reload-rules
Finally - relogin.
Run solaar pair and follow instructions to pair a mouse or keyboard.