Tend to agree that the OP was not stranded. They had an alternative train, which was the next LNER one, and one which was communicated to them. Whether that communication was clear or not is open to debate but it’s not the main issue here.
Define "stranded"! 28.2 doesn't use that word.
Perhaps you're thinking of the old NRCOC which said:
"If disruption caused by circumstances within the control of a Train Company or a Rail Service Company l
eaves you stranded before you have reached your destination printed on or stored on your ticket,
and the Train Company whose trains you are entitled to use is unable to get you to that destination by other means, any Train Company which is in a position to help will, if it reasonably can, either arrange to get you to that destination, or provide overnight accommodation for you."
The new 28.2 is a lot broader - "Where disruption prevents you from completing the journey for which your Ticket is valid and is being used, any Train Company will, where it reasonably can, provide you with alternative means of travel to your destination, or if necessary, provide overnight accommodation for you."
The pieces in bold have gone - Lumo gains an obligation to assist irrespective of whether or not LNER would also be able to do so - the precondition has gone. Was there disruption? Yes - the only train on which the ticket was valid didn't run - so 28.2 kicks in. The fact that LNER is also offering an alternative does not mean Lumo doesn't also have an obligation.
Further, the Advance ticket T&Cs state unambiguously "Tickets are valid ONLY on the date and train service(s) shown on the ticket(s)". No ifs and buts - the ticket is only ever "valid" on ONE service. The provision "If delays occur while travelling, you will be allowed to take the next available train(s) to complete your journey" is not qualified by operator and doesn't override the definition of "valid".
Or to put it another way, this whole area has turned into an inconsistent mess of overlapping provisions which aren't necessarily aligned with common custom and practice and where each party can find something to support their point of view and it's anyone's guess what conclusion a court would reach in any particular circumstances!