Linux does not work very well on the USB-C Macs. Apple has made a lot of changes to the hardware and Linux doesn't have the necessary drivers to work with everything. Your best option for running Linux on a USB-C Mac is by installing Linux into a Virtual Machine. This is much safer to your macOS installation and much less clumsy and awkward than rebooting all the time.
If you do need to install Linux on the bare metal for the extra performance, then install Linux to an external USB3 drive so that you leave your internal macOS SSD installation untouched. Modifying partitions on any drive, but especially on a boot drive is extremely risky plus users almost always choose the wrong sizes for the partitions which usually ends up with the user needing to erase the whole drive and starting over.
To install Linux on the bare metal you will need the latest version of Ubuntu 20.10 in order to have the most recent drivers available for the USB-C Macs. Keep in mind that many things will not work such as WiFi. Also you will need to use a wired mouse to be able to choose between trying out Ubuntu from USB or to install Ubuntu. After you make this selection you should be able to use the built-in Keyboard and Trackpad. You will also need to boot into Recovery Mode and use the Startup Security Utility to change the security settings to "No Security" to allow non-Apple OS to boot and to "Allow booting from USB":
https://support.apple.com/en-us/HT208198
Here is some information and details on the Linux status for the various USB-C Macs:
https://github.com/Dunedan/mbp-2016-linux