Thanks, all, for your comments. I did figure that iOS was going to be a bit of a challenge compared with macOS, for example. The nice thing about the browsers on macOS is that (with the exception of Safari), they all support Proton VPN’s browser extension, so I can effectively separate my activities not only across different browsers, but also across different VPN servers and therefore, IP addresses as well.
Seems the best I can do in iOS might be different browsers for different use cases. But I can’t do much about leveraging multiple IP addresses. It will be interesting to see how the browser companies leverage their own web engines in the EU App Store!