

I’ve been using NixOS on my server. Having all the server’s config in one place gives me peace of mind that the server is running exactly what I tell it to and I can rebuild it from scratch in an afternoon.
I don’t use it on my personal machine because the lack of fhs feels like it’d be a problem, but when selfhosting most things are popular enough to have a module already.
Is it likely? No. Is it possible? Yes.
If you want to make absolutely sure that Windows can’t spy on anything, you’ll need to physically remove the storage device containing Linux when booting.
A more practical but slightly less secure approach is to enable full disk encryption on Linux. Then, if Windows does decide to get sneaky it’ll only see random data.
This doesn’t prevent hostile code such as ransomware from destroying the data though. For that, you need to have good backup hygene.
A good backup system is to have automatic daily backups to some online cloud storage provider, and weekly or monthly backups to a physical device you keep disconnected and safe.