I am an Indian citzen, and have a Schengen visa that is valid from 28/09/2023. My flight departs from New Delhi on 28/09/2023 at 02:50 AM IST (that will be some time 27/09/2023 in Germany) and lands in Frankfurt on 28/09/2023 07:50 AM Frankfurt time. Can there be any problems with the boarding? The carrier is Lufthansa.
That should be fine. A visa needs to be valid at the time of arrival and yours is.
Your visa will also be checked during check-in in New Delhi. I have encountered check-in agents who (despite working for international airlines) have trouble with the concept of time zones, so you may get some questions about it. If that's the case, just state that the "my visa is valid at the arrival time in the arrival time zone". That should suffice.
However, that's unlikely in your case since the it's already 9/28 at your departure as well.