Thanks for sharing, but I'm curious what problem this solves. You're clearly stating what type of solution it is in "it's purpose is to make it easy to manage many browser profiles on one system."
But why am I looking for this solution? I personally use Chrome, and sometimes have to test things on Firefox, but that's either one-offs or using Puppeteer.
The closest I get is under the Default Browser feature: "Forget about opening links in the wrong browser. Donut Browser will allow you to choose what browser you want to use for each link."
Perhaps some example where you've found the default browser feature useful?
Sorry, just saw your comment. Copying from another thread, I use it to more privately browse the web, separate my personal and professional accounts, and manage links. For example, when I open OneDrive link, I don't want it to open in my work profile. It's not a big deal, but it allows to keep personal and professional lives a little better.
Also, since the ads companies are migrating from solely using your IP and cookies for tracking to creating a comprehensive browser fingerprint, it allows you to better control what data you feed to them.
I got 5 browsers installed each has different extensions and I use browser profiles.
This could help me, once its released on linux I give it a shot