Yeah, they do need to clean up the installer a bit. It's also not quite turnkey for a Windows dual-boot.
Mind letting us know why or how? When I installed it almost a year ago on my desktop, I did install it as a dual boot option with no issues. Of course this doesn't mean there aren't issues I just didn't run into. I'm also not new to Linux and didn't pick a fully default install, if that makes a difference. So I could've probably fixed it if it did break, but it never gave me any issues.
The only thing that I dislike, and that could probably cause issues, is that for my installation the mount point for the efi/boot partition isn't specified in fstab using a uuid, but using the device name (which isn't fixed and can change with hardware changes). That is a very weird (and unnecessary) decision IMHO.
If you're using a keepass database, Keepass2Android can natively sync with many cloud options including self hosted and generic ones, even without specific "companion" apps. That's what I use. In my case, it's backed by my NextCloud, but it used to be Google drive before.
Just also sync the file on your PC, merging changes from different clients is part of the keepass database format and "just works".
Also VaultWarden works great if your can self host it, but I prefer keepass for a variety of features and integrations.