on my Ampere server with an OS installed, trying to load different OS via virtual media mounted ISO but observed that server does not boot from this mounted ISO and it ignores this.
Only option is to update boot order to CDROM manually. Is this an issue with OpenBMC ?
Virtual media does not alter the UEFI boot order; it only mounts the ISO. The host will disregard the virtual CDROM unless your platform allows for appropriate BootSourceOverride via Redfish and the firmware respects it.
The majority of Ampere devices still need manual BIOS boot order changes. That is not an OpenBMC problem; rather, it is anticipated behavior.