"The RTC battery is low" + Inactive keyboard

Hello everyone!

For the past few days, I've been racking my brain over a Toshiba Satellite C875!

Indeed, I need to install a system on it, but booting is complicated with Toshiba.

So I decided to reset the BIOS, remove the battery, press the ON/OFF button, etc.

But nothing works; I get the message "The RTC battery is low" F2 to configure.

The problem is that no keyboard responds, neither the laptop's nor an external one via USB.

If anyone has a solution, please! Because I'm truly stuck here...

Thanks in advance.