To find out the current version of Linux kernel running on your system, use the following command.

uname -sr

Linux 4.19.0-8-amd64

To list all installed kernels on your system, issue this command.

dpkg --list | grep linux-image

ii  linux-image-4.19.0-6-amd64    4.19.67-2+deb10u2           amd64        Linux 4.19 for 64-bit PCs (signed)
ii  linux-image-4.19.0-8-amd64    4.19.98-1+deb10u1           amd64        Linux 4.19 for 64-bit PCs (signed)
ii  linux-image-amd64             4.19+105+deb10u3            amd64        Linux for 64-bit PCs (meta-package)

Do the same for kernel headers:

dpkg --list | grep linux-headers

Run the commands below to remove a particular linux-image along with its configuration files, then update grub2 configuration, and lastly reboot the system.

sudo apt remove --purge linux-image-4.19.0-6-amd64
sudo update-grub2
sudo reboot