If all you need to do is put the photos into a repository where you can browse them, but don’t need to do any photo editing, you might want to consider Adobe Bridge, which is free. Bridge is Digital Asset Manager (DAM) software you use to view, organize, tag, and add metadata to creative assets, which includes photos.
Although Adobe designed Bridge to work with its other Creative Cloud applications, you absolutely do not need any other Adobe programs to use it if all you’re doing is browsing and organizing photos.
You also don’t need to export photos from Lightroom to Bridge. Bridge is a file browser—all you need to do is point it at the file folder(s) where the images are stored. When you cancel your LR subscription, those file folders aren’t going to go anywhere—they will still be on the drive where they’re stored. You won’t be able to use LR’s library file, which is where the program stores the information used to create LR collections as well as metadata, but the photos themselves won’t be lost.
If your family member stored their photos in labelled folders—e.g., all the photos from, say, their trip to the Grand Canyon are stored in a folder labelled “Grand Canyon Trip”—that level of organization will survive no matter what.
But here’s a slight complication: If your family member added tags (“keywords” in LR parlance), titles, captions, copyright info, etc. to their photos, I believe that that information can only be viewed in Bridge if the files are in JPG format. If the photos are in RAW format, you will need to export them to JPGs first to see them in Bridge (or any other program, for that matter). Exporting JPGs from LR isn’t particularly difficult, but you’ll need to make sure that you’ve told LR to export the files with all the metadata attached.
I think I’m making this sound more complicated than it is, but you’ll be able to find plenty of tutorials online to help. (Or, just ask a chatbot …)