dmesg shows "rtc-pcf85063 ...: error -EREMOTEIO: RTC chip is not present"

This is expected and harmless on FIBER Lite — it means the Configure Hardware step was followed using the CM4-based FIBER guide's config.txt block verbatim, including the external RTC overlay line. Remove any dtoverlay=i2c-rtc,... line from /boot/firmware/config.txt and reboot; the Raspberry Pi 5's native built-in RTC (rtc0) does not need it.