Well, since SearXNG aggregates results from more than 70 search engines and not solely Google, it’s a safe bet they’ll be fine regardless of Googles moves. However, sourcing results from Google may be impacted, but they still have many other options built in aside from Google. Whoogle being a proxy only for Google makes it reliant on Google, so their upstream changes will be very noticeable. This being the case, I’d say switching to SearXNG is going to be the best move as it has redundancy built in making it not dependent on any one engine.
I just learned the dev of Phoenix forked Mull! It’s called IronFox (https://gitlab.com/ironfox-oss/IronFox) and has a F-Droid repo. I’m pumped on this, thanks a bunch for highlighting all this and to the original commenter for providing the link to Phoenix!