This has been bugging me. I was absolutely confident a (non-super) nova was an expected event in the evolution of sun-mass stars. Currently, though, the scientific term "nova" (excluding supernovae) clearly is applied only to a situation with binary stars, where a white dwarf siphons off matter from a less dense but heavier companion star. There are other specific things that happen to solar-mass red giant stars, such as helium shell flash, a rapid but short-lived change in brightness that can also leave a planetary nebula. Such an event could sound like it meets the definition of a "nova" but it doesn't meet today's technical definition of it.
It seems like the assignment of "nova" to a common stage of solitary low-mass stellar development is outmoded, so a change in nomenclature could help explain my confusion. For instance, this 1986 book https://archive.org/details/privatelivesofst00gall/page/68/m... states "Stars called novae explode and grow much brighter over a period of days or weeks, then return to normal again, usually over several years. Although we have ideas about nova stars, we have a lot more to learn about them. [...] When a red giant collapses and is well on its way to white dwarfhood, it may go through one or more periods of being unstable. At such times the star may erupt as a nova. This may be especially so of the more massive stars."