An owner can put in as much money as they like. But it's not classed as revenue, which can be spent on players and other operating expenses. Sheikh Mansour can give us £1bn in cash but we can only spend what we earn from TV, tickets and the various forms of commercial income.
Owners can cover limited losses (currently €30m over any 3 year period, which is due to increase to €60m from 2024. They can also sponsor clubs but only if that's in line with what an unconnected source would have paid.
The whole premise of UEFA's case against us was that the Etihad & Etisalat sponsorships were simply a device allowing Sheikh Mansour to shovel extra cash in. When this was challenged at CAS, it was shown that (a) the sponsorships met the fair value test and (b) in any case, the additional cash hadn't come from ADUG.