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.
Here’s the most recent example:
It should be noted that the advertisers get zero personal information, neither does Mozilla, and it has been designed in a way so that the data is impossible to fingerprint in a way that can tie it back to any individual person, machine, or specific location.
It’s a way for advertisers (and like it or not, a decent amount of the content we want has to be paid for somehow) to see how effective their ads are without anybody’s privacy being encroached on.
Should it have been turned on without informing the user? Fuck no. But there’s a lot of misinformation going around about this.
Personally I’ll still be using uBO, because I despise any ads at all, but if we are to have ads, the system Mozilla has built is just about the most ethical and privacy-respecting way to do it.