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.
Because it’s not based on chromium(blink web engine), there are two other well supported web engines which browsers can be based on, WebKit (Apple), and Gecko (Mozilla).
At the end of the day, if it’s built on Blink, it’s liable to have Google break things they don’t like on the back end. Including ad blockers.
Opera used to be built on it’s own web engine (presto) but since 2013 it’s been built on Blink.
that was a great summary, thank you
trying to research such a broad topic was overwhelming