UBI would be paid to everyone. The essential workers would be paid on top of it because they are still able and engaging in maintaining their part of their employment contract by providing essential services and goods. If you can’t maintain the employment or benefit contract due to the industry/government service being unable to operate (as an employee or employer, a pensioner, a universal credit user) you go on UBI.
If you pause the economic model of transactions for tangible services (so work, utilities, finance, travel, tax, NI, housing contracts etc) it means business aren’t losing money, they are essentially paused as their payroll, premises, costs and productions are paused. At the moment society only needs to fulfil the bottom level of Maslow. You meet the cost for shelter, food, safety, health for everyone for that acute period of time. We had enough money in the pot, as a country, to do that for 3 months if not more.
The economy is just a tool that we use as humans to innovate, improve and make our lives more comfortable and fulfilling and create opportunities. We can’t really use that tool effectively now due to being stuck in a short frame of time where the threat to life means our opportunities are limited. We have all managed to psychologically pause our normal way of living (even essential workers have less opportunity because everything is closed to them apart from work) I don’t know why it was unacceptable to pause a tool that we use.