The audio, microphone and wifi don't work out of the box with Ubuntu 19.10 on a Lenovo ThinkPad X1 Carbon 7th Gen laptop. Here are the steps I made to fix them.

Update: I upgraded to Ubuntu 20.04 and now everything works with the default settings. I'm on kernel 5.4.0-26-generic and reverted my changes to /etc/modprobe.d/blacklist.conf and /etc/pulse/default.pa (steps 3 and 4 below).

Note 1: Even if I tried to make as little customization as possible to make the upgrade easy to Ubuntu 20.04 when it's available, there may be other more elegant ways to fix the issues.

Note 2: The wifi works with kernel 5.3.0-18, which is the kernel that comes by default with the Ubuntu installer. However, the wifi doesn't work with the more recent kernels installed by Ubuntu 19.10. So if you lose wifi while doing these steps, make sure you boot with kernel 5.3.0-18.

Step 1: Install the latest kernel available from kernel.ubuntu.com

Use ubuntu-mainline-kernel.sh to install the latest kernel available from kernel.ubuntu.com.

Note that Ubuntu 20.04's kernel (kernel 5.4) doesn't solve the issues. So we are forced to install a mainline kernel. Not true. I upgraded to Ubuntu 20.04 and it works with kernel 5.4.0-26-generic.

Step 2: Upgrade linux-firmware package to Ubuntu 20.04

Download and install Ubuntu 20.04's linux-firmware package, which is currently at version 1.187.

Step 3: Blacklist snd_hda_intel and snd_soc_skl

Add the following lines to /etc/modprobe.d/blacklist.conf:

blacklist snd_hda_intel
blacklist snd_soc_skl

Step 4: Update PulseAudio config

Add the following lines to /etc/pulse/default.pa:

load-module module-alsa-sink device=hw:0,0 channels=4
load-module module-alsa-source device=hw:0,7 channels=4

Step 5: Reboot

Reboot and make sure you boot with the kernel installed in step 1.