linux on macbook air 2018

Hello,

Have anyone succeeded in disabling "secure" boot on macbook air 2018 (or similar models)? This is obviously needed to at least run a linux liveusb, and there are online instructions saying that this is possible (like this one:
https://www.omgubuntu.co.uk/2018/11/...ant-boot-linux
or an instruction from apple:
https://support.apple.com/en-ca/HT208330
), but none of them seems to work: any attempt to boot linux from a liveusb fails exactly as with "secure" boot enabled.

My day job is working with Macs, and my advice is to run Linux as a virtual machine "guest" under the MacOS "host". The new T2 chip will prevent you from installing Linux as a native operating system.

Dell XPS13 has similar hardware specs to the MacBook but comes with Ubuntu Linux preinstalled. Highly recommended.

I know about all of the approaches you suggested, but this does not answer my question: do the instructions from omgubuntu or apple work at least somewhere?