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.
They should I’ve been using mull on mobile and Librewolf on Windows 10 since the first time Google announced these Anti Adblock intensions. Must be a few years now.
I did mess with Thorium a little when it claimed to be the fastest browser on earth but yeah apart from that I’ve been using hardened Firefox forks