I believe that the whole concept of "software without support" is fundamentally flawed.
I have been asserting exactly the opposite in this thread.
None of which are insignificant.
In addition to that you must now support (and test for) a million configurations, rather than just one.
I also have experience developing and maintaining cloud solutions. Total amount of work that goes into large cloud apps and amount of things things that can brake or not work properly is fairly impressive. Definitely not any less then on premises
But they will expect it.
In my case for example I have few older products (desktop apps that still sell and bring some money) for which I have source code that has not been touched for years. Not interested in development new features either as those apps are mature and there is not much ROI in developing new features the whole 2.5 customers are willing to pay for.
Long story short I do not have any critical bugs there. Maybe do exist and hiding somewhere but since nobody had ever discovered them I am totally cool. The only occasional customers complaint I have every once in a while is RTFM type. Not real bugs.
Which makes sense IMHO, provided they are not expecting any updates to their on-prem installation. It can just be a fork of your current codebase with no new features or warranty. Maybe you can include some terms for critical security updates but that is about it.