I wish language selection in OS and Browser were easier to access... but your browser does send a language header with your request, which generally matches your browser.
Location based is and can be a pain. I live in a border state and often get spanish versions of sites... I also follow a couple prominent youtubers who post english and foreign language content, so sometimes get results in those languages, that I don't read.
That said, using the default for the browser, and allowing override isn't a bad thing... I usually look for something that looks like a flag in the upper right, for language selection. And the few times I've written multi-language sites/apps that's the UX I prefer to use. I would default to browser/header, I would respond to the change event, and if the user selects a preference, set a cookie and use that first.
Again, I do wish it were easier to switch for the browser itself.
1. https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Ac...
2. https://github.com/i18next/i18next-browser-languageDetector/...
3. https://github.com/i18next/i18next-browser-languageDetector
4. https://developer.mozilla.org/en-US/docs/Web/API/Window/lang...
