Enable Uart on raspberry pi 4 Ubuntu core 22

Hey guys. I want to enable uart on raspberry pi ubuntu core 22. I test this link to do it but it does not work for me:

I can’t find cmdline.txt and config.txt in /boot/uboot and I cant create a new file on /boot/uboot because the file system is read-only. thanks for guiding me.

I solve it. In ubuntu core 22, config.txt and cmdline.txt files moved to /run/mnt/ubuntu-seed/