Negotiations between conflicted parties have to first recognise...

Negotiations between conflicted parties have to first
recognise the other's position and then probe areas
of common agreement and then compromise on
the remainder. Usually both parties have base
red lines where they are not willing to compromise.

In this case Russia would need enforceable assurances
the Crimea remains Russian and that Russian Speaking
Ukrainians (now Russian citizens) in Donbas are
fairly treated by having a major share of autonomy.

The Ukraine would want its pre 2014 borders restored (Crimea excepted)
and the removal of Russian troops from the pre-2014 Ukrainian mainland

Given the shenanigans by both sides from Minsk 1 to the invasion,
it will be difficult to engender the necessary degree of mutual trust
in order for these negotiations to start which leads me to think,
one way or another that the Ukraine will end up a rump state
which Russia will use as an example for Georgia, Moldova
or Belarus should they consider going the way of the Ukraine
post 2014.

Perhaps NATO (Lithuania) blocking the land corridor between
Russia & Kaliningrad via Lithuania would give NATO (Ukraine) an extra bargaining
chip at a future negotiating table?