Edit: it appears the PWA support in Firefox is not ideal, see responses to this comment.

Chromium is not an offshoot of Chrome, it's more of a precursor to Chrome, and it is completely controlled by Google. As such, it will also drop support for extensions that do not support Manifest v3.

If you want to enable PWA support in Firefox, it looks like this is possible (however the experience doesn't seem to be great, see responses to this comment): https://developer.mozilla.org/en-US/docs/Web/Progressive_web_apps/Guides/Installing

For other browser suggestions see, e.g. https://www.xda-developers.com/4-browsers-manifest-v2-ublock-origin/

They are deprecating the underlying technology(called manifest V2 or MV2 for short) and replacing it with a different one(MV3) that lacks some of the capabilities for some kind of adblocking.

So yeah, it’s pretty much dead on chromium. The developers of brave have commited to provide a best effort support for their browser though: https://brave.com/blog/brave-shields-manifest-v3/

Firefox on the other end has no intention of deprecating support for MV2 so any browsers based on that are fine. Keep in mind MV3 supports some adblocking and some Adblockers have already moved to it, it’s just a lesser extent.

MV3 doesn't make adblockers impossible, only less effective. It's important to note that MV3 has changed a fair bit since the initial controversy and isn't quite as limiting as it used to be. The fact that adblockers will lose some functionality at all is still a dealbreaker for me and many others which I thankfully won't have to deal with as a Firefox user, but it isn't going to kill adblockers on Chrome and most users will probably just install an MV3-compatible adblocker and move on with their day.

uBlock Origin's developers don't seem to want to make a proper MV3 port, which is fair because they'd probably have to rewrite most of the extension, but they did create the far more minimal uBlock Orgin Lite, which a lot of people have taken to be an attempt at porting uBlock Origin to MV3. It isn't that. On top of MV3's limitations, it also makes the decision to work within these self-imposed restrictions:

• No broad host permissions at install time -- extended permissions are granted explicitly by the user on a per-site basis.

• Entirely declarative for reliability and CPU/memory efficiency.

These aren't MV3 limitations, just a thing Gorhill decided to do. See the FAQ. You can get much closer to uBlock Origin within MV3's constraints than uBlock Origin Lite does. Right now, the best option appears to be AdGuard, which has been making a true best-effort attempt at porting their adblocker to MV3 pretty much since the announcement.

So, is Chromium going to go the way Google wants it to go for Chrome? It was my understanding that Chromium is kind of an offshoot and not just up to Google in terms of its course.

I would be surprised if it doesn't. Chromium isn't an offshoot, it is the primary base of Chrome; it is a Google project at its core, and they essentially fund and build upon the open source efforts of the community to make Chrome.

I wonder how ungoogled-chromium is faring?

Chromium itself will. Other Chromium-based browser vendors have confirmed that they will maintain v2 support for as long as they can. So perhaps try something like Vivaldi. I haven't tried PWAs in Vivaldi myself, but it supports them according to the docs.

Here is another concerning reason to not use Chrome.

https://www.bleepingcomputer.com/news/google/google-chrome-to-let-isolated-web-app-access-sensitive-usb-devices

You can use webapp Manager to get web apps for Firefox and apparently official PWA support is also coming

Another approach to webapps in Firefox is to create separate browser profiles and create shortcuts for them.

Firefox *might* be *thinking* about bringing back webapps: How can Firefox create the best support for web apps on the desktop?

so you have to decide: you want websites inside their own window with a nice icon, or you want to get ridd of ads.

if the first is imperative to you, the choice is simple. watch ads.