EDIT: Apologies. Updated with a link to what gorhill REALLY said:
Manifest v2 uBO will not be automatically replaced by Manifest v3 uBOL[ight]. uBOL is too different from uBO for it to silently replace uBO – you will have to explicitly make a choice as to which extension should replace uBO according to your own prerogatives.
Ultimately whether uBOL is an acceptable alternative to uBO is up to you, it’s not a choice that will be made for you.
Will development of uBO continue? Yes, there are other browsers which are not deprecating Manifest v2, e.g. Firefox.
The single biggest security improvement you could make for Beth in accounting would be to install UBO. Where do you think she gets all those shitty toolbar extensions? That’s right, from ads.
This is targeted at destroying adblockers because Google is, first and foremost, an ad serving company. That’s their business model. It incidentally improves security for certain users in certain edge cases, because they need some kind of figleaf of legitimacy.