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.
I switched to Firefox last year when talks of chromium manifest V3 First started popping up. I had used Firefox many years ago when Chrome was first coming out. I was blown away at how well it worked compared to old Firefox, plus how easy they made it to switch. I even changed my phone browser and my desktop browser ties in with it seamlessly. Very happy with the switch and I wish I had switched earlier.
Now, I just wish I could use it at work. Not sure how I’m going to block ads on my work browser.