The use for donations could be for a single person whose job is to check the upstream code for any antifeatures (telemetry, ads, product placements, online service defaults, Google as paid default search engine, etc.) not in the user's interest and revert them, as well as bundling any useful extension like uBlock Origin and verifying them.
That needs minimal effort compared to building a browser, because it doesn't involve doing any of the hard work, but just removing code that serves to line the pockets of those doing most of the work at the expense of the user.