Choose browser
"and b) if you wanted to use a chrome-based browser for some reason there would be no easy way to choose DDG as the default (or at least this was true the last time I tried to use a chrome-based browser on android)."
You can just download Brave and Firefox apps (or even DDG I think?) and set one as default browser and make search engine choices from there - DDG and Startpage for me usually.
I go further and delete Google from my android phone completely which is not for everyone but normally, depending on the phone, it is not that difficult to get rid of the google browser.