Although GoodNotes 5 is not available for non-Apple devices at present, such as those on Android, Chrome or Windows based operating systems, it is possible to view your notes on such devices if the need arises.
The quickest option is to share a specific document on the web, which can be accessed in any browser.
If you wanted to view existing GoodNotes 5 files on a non-Apple device, you have the option to enable Auto Backup in PDF format with a supported cloud service (i.e Dropbox/Google Drive/OneDrive) to view your notes on a non-Apple device/machine.
Or alternatively, you could look to export your files to your non-Apple device, either via a Manual Backup or via alternate means such as email or messaging services etc. However, please bear in mind, that if you send your files as .goodnotes format, your non-Apple device will not be able to read them, as such it is important they are either exported as PDF or image.