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 only use Firefox and have for the past few years. Yesterday I tried to schedule an appointment to get my oil changed at the dealer but was unable because the process on the site just flat-out breaks on Firefox. This is not a complaint about Firefox, but the fact that Chrome is so popular that some websites only work with Chrome. I don’t have a Chromium-based browser installed (besides Edge, which I’ve never opened intentionally) and I despise being on the phone (which is why I was trying to schedule online in the first place), so I just didn’t make the appointment. I’ll go somewhere else to get my oil changed. Sorry for the rant but it was extremely frustrating.