I've solved it myself, and I decided to share it here in case there are someone out there wanting to compile their own kernels for Deepin.

I started out with Deepin 20.8, running kernel 5.18.17-amd64-desktop-community-hwe. This kernel lacked support for both my bluetooth and webcam, so I needed to compile a new kernel after having modified those drivers.

1. Download the appropriate kernel source from here https://kernel.org/
   For me that meant 'wget https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/linux-5.18.17.tar.gz' into ~Downloads
2. Next, I install the correct header files: 'sudo apt install linux-headers-5.18.17-amd64-desktop-community-hwe'
3. Unpacking the source with 'tar zxvf inux-5.18.17.tar.gz'
4. Then I modified the files in drivers/bluetooth and drivers/media/usb/uvc to enable the devices I was missing
5. In linux-5.18.17, run 'make mrproper' to clean the source tree for old configs
6. In linux-5.18.17, run 'yes '' | make localmodconfig' to take your current (running) .config and turn off any unused modules without asking all the questions
7. To prevent the new kernel from getting the same name as the running (original) kernel, give it a dedicated local version by editing .config just created in item 6.
   Here's my part of the .config:
   CONFIG_LOCALVERSION="-amd64-desktop-community-hwe-blix"
8. Next, start the compilation with 'make -j$(nproc)'
   This will use the amount od cores your PC has available to speed up the compilation
9. After a successful compilation:
   'sudo make modules_install'
   'sudp make install'
   'reboot'