The basic answer is, like everything else, it's up to you as the DM to decide. There are no explicit rules for extending immunities to general actions or conditions, nor is there any specific description about what being immune to some kind of damage looks like.
In a game I was running, I would rule that a lycanthrope can't be harmed by a guillotine.
Crawford summed it up perfectly:
A lycanthrope's immunity is a supernatural resilience against the attacks of regular mortals.
I would discourage the characters from any kind of methodical experimentation to determine the limits of lycanthropic immunities. Tonally it's not the kind of story I want to tell; I run D&D games to tell fantasy stories, and determining how a wererat's immunity to weapons interacts with physics is science fiction. Likewise, in-game, it's not how inhabitants of the world, including the player characters, would interact with magical things.
Consequently, I would adopt the general principle that without the aid of magic or divine forces, the tools of ordinary mortals cannot harm a lycanthrope. The lycanthropic aversion to silver is a matter of divine edict, and part of the nature of were-creatures.
Consequences of this would be that a guillotine blade doesn't cut or crush a lycanthrope. A great stone lifted by mortals will bounce off it; driving a wagon over it will leave it tumbled and dusty but unharmed. And so on. Lycanthropes are horrific, unnatural things that are beyond the reach of ordinary mortals. It shouldn't be possible to truss them up and butcher them as if they were just brigands wearing masks.
I would, however, rule that the natural world can harm and kill a lycanthrope. So if mortals can throw it over a cliff, or into a volcano, or immolate it in a bonfire, or manacle it to a pier as the tide comes in -- those things might kill it. There, it is the world itself that's harming the lycanthrope, not the artifice of mortal beings.
I would also make lycanthropes difficult or impossible to capture and imprison without use of magical or silvered restraints. Remember that all lycanthropes are shapechangers — any bindings that would secure a wererat in human or hybrid form would fall harmlessly away when it assumed rat form!
However, your campaign, players, and style may be very different.