Well I'd lay the ground by asking to talk seriously if they're totally clueless about how you feel. Say you're not happy and why. If you are looking to jolt them into a response or acknowledgment, that should be enough.
If you think both of you are unhappy and things have just drifted along, but you see a way through, suggest counselling.
If you feel the relationship is dead in the water, give them notice - I'd prepare alternative place to stay for myself if alone, or if staying with dependent DCs, give adequate time for OH to leave.
Never use DCs as emotional weapons. Ensure you both recognise the need to keep things on a good footing for the family.
If you have teens home or away, if you are paying uni fees you still need to stay on reasonable terms so try and keep business like and not vengeful.
Secure finance for yourself but don't fleece your STBX.
It sounds ideal paying nice compliments to your partner to soften the blow of farewell and promise friendship and civilised contact. But if they are at all unwilling to let go they can twist what you say and argue you are giving mixed messages. Sometimes where you are not bound by children it is kinder to detach rather than give false hope.