I got rootfs from the SDK1.8 virtual machine, but only linux5.4 can't start with linux4.19.Thank you very much and I am looking forward to your reply!
NXP offers SDK Yocto with LSDK Components:
https://source.codeaurora.org/external/qoriq/qoriq-components/yocto-sdk/about/
Use the gatesgarth or dunfell branches for your board.
This SDK supports the P2020RDB board.