Don't install Linux to the internal SSD. That will almost always result in something going wrong since people tend to realize they don't have enough room on one or both partitions.
Plus Linux doesn't not run very well on 2018+ Macs due to the T2 security chip plus the proprietary hardware Apple uses on them. Most likely WiFi will not work, plus there may be some other built-in hardware which will not function. See these articles for some of the issues with running Linux on the Apple USB-C laptops including a couple articles specifically for the 2018-2020 T2 Macs (I don't know if these are still being updated). I'm sure there are other sites out there with similar information about these USB-C Macs (you need information specific to a 2020 model or at the very least 2018-2020 models).
https://wiki.t2linux.org/
https://github.com/Dunedan/mbp-2016-linux
https://gist.github.com/roadrunner2/1289542a748d9a104e7baec6a92f9cd7?permalink_comment_id=2969196
If you want to try using Linux on a USB-C Mac (actually any Mac or actually any computer), it is best to use Linux in a VM as others have suggested. If you really need to run Linux on bare metal for some reason, then it is best to install Linux to an external USB3 SSD although for a T2 Mac you will need to use the Startup Security Utility to modify the Mac's security settings to allow booting from USB. For most people, running Linux in a VM is more than sufficient and will be much easier.
