It used to be Mac-only, because the work is done by driving a real browser on a real desktop and that part was written for one operating system. It is written for both now.
It needs macOS 14 or later. Everything lives in a Mind My Money folder on that Mac, so a Mac that isn't your daily machine still works.
There's a free iPhone app, and it won't help here: it has nothing of its own and shows nothing until a Mac has written its first report.
Windows 10 or later, 64-bit. Nothing in it is locked, and you pay what you decide it is worth, including nothing.
Nothing to sign up for. If you want to hear about releases anyway, your account page has the switch.