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.
It’s the Internet Explorer problem all over again, but this time from an even more invasive company.
The more people choosing non-Chomium browsers, the better. Keeping them popular enough that most sites have to support them is the only way to preserve what little agency people still have on the mainstream web.