Yeah I'll probably have a big tax bill if I ever renounce citizenship. I haven't thought about it too much yet since it's still my only citizenship, and I have a lot of friends and family in the USA. Like a visitor visa might be fine in normal times, but I wouldn't want to rely on it in an emergency today given how visitors are being treated lately.
'Till now I was always able to just do financial planning myself, but I really should hire a professional.
The extension I ended up using for Firefox was Straight to the Web. Auditing the source code I saw that it looked for certain Google URL patterns being navigated to and re-wrote them.
I just tested with DuckDuckGo's "!g" feature and it seemed to work, but I don't use DDG so I don't know if there's anything I'm missing.