When you install it to a system with other partitions or drives that are accessible, it silently autoencrypts them all using Bitlocker which is now on by default.
It's not too bad unencrypting your C: volume afterward with a few clicks, but if you don't have a Microsoft Account then you won't have a readily available key (to type in) or easy decryption option for the other volumes. It can be a lot easier to reformat and recover those non-C: volumes from backup than bother to decrypt, you've got to virtually overwrite the entire drives anyway :(
Simply installing the latest Windows is definitely more likely to be the direct cause for loss of more gigabytes than most malware I've seen.
I assign the standard Linux GUIDs on non-Windows volumes to be sure, as appropriate even though the regular "Basic Volume" GUID is often found since it works "for all".
The standard Linux Partition_type_GUIDs as shown in Wikipedia (please refer to it) after expanding ("show") the condensed table:
4F68BCE3-E8CD-4DB1-96E7-FBCAF984B709 for the OS root
0FC63DAF-8483-4772-8E79-3D69D8477DE4 for data
8484680C-9521-48C6-9C11-B0720656F69E for usr
0657FD6D-A4AB-43C4-84E5-0933C84B4F4F for swap
These can be SET ID from Windows, plus you can set GPT Attributes to hidden and/or readonly temporarily because it is getting more difficult to trust Windows so that's why I'm experimenting so much.
Also you can safely change the ESP volume GUID from standard to basic, and Windows will most likely still boot normally on many PCs, you can then assign a volume letter to the ESP and after another reboot have full admin access to the ESP and its black pearl, the EFI folder within, from the GUI.
When you install it to a system with other partitions or drives that are accessible, it silently autoencrypts them all using Bitlocker which is now on by default.
It's not too bad unencrypting your C: volume afterward with a few clicks, but if you don't have a Microsoft Account then you won't have a readily available key (to type in) or easy decryption option for the other volumes. It can be a lot easier to reformat and recover those non-C: volumes from backup than bother to decrypt, you've got to virtually overwrite the entire drives anyway :(
Simply installing the latest Windows is definitely more likely to be the direct cause for loss of more gigabytes than most malware I've seen.
It didn't used to be this way.