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.
So many kids with assigned school Chromebooks are going to get fucked over by this. You can apparently install Firefox on a Chromebook via the Google Play Store, but that was disabled on my daughter’s Chromebook. I don’t want her exposed to constant advertising while she’s doing her schoolwork. It’s bad enough that she’s exposed to it the rest of the time just being in America.
How about a DNS-based ad-blocking service? NextDNS is pretty good and not expensive. You should check if you can set custom DNS servers on that Chromebook, though.
DNS over https bypasses much of that, right? till you find and block those DNS servers