My understanding of the rules relating to Universal Credit (as far as unemployment is concerned) is that the main provisions of the rules which related to Job Seekers' Allowance still apply.
That means that an adult who is unemployed, with a full National Insurance record over recent years and who is genuinely seeking work (and prepared to go through all of the relevant hoops, such as regular attendance at a JobCentre) is entitled to receive £73.10 per week (assuming that they're at least 25 years of age and that their partner isn't also claiming) for up to 6 months. That entitlement is NOT means tested.
However, when applying for the benefit, you still get asked about your means in case the 6 month period expires. At that stage an unemployed person who is living with a spouse or partner often loses all of their benefit (or, at least, most of it) because means testing then comes into effect, with the partner's income being taken into account, as well as the savings of both the claimant and their partner.
When a person voluntarily leaves their job there's a buffer period before they can start claiming benefit.
One important change that has come about with the transition from JSA to UB is that, while JSA counted as taxable income, UB does not.
The calculators here might well help:
https://www.gov.uk/benefits-calculators