Apple announced that macOS 28, which will be released in 2027, will not support encrypted HFS+. The support document simply calls it “Mac OS Extended file system”. You may want to double-check old archival HDDs if they’re still formatted to encrypted HFS+. I’d recommend simply reformatting the drive to encrypted APFS, though decrypting the volume is an option too.

Realistically speaking, most users go unaffected. Data saved on encrypted HFS+ drives is likely old enough to be quite meaningfully light compared to modern media. You wouldn’t need to buy a 10TB drive to rehome it. Likely you would be consolidating the contents into one big drive instead of a multitude of them. And it will be a necessary expense. Archival data doesn’t simply survive without maintenance. Without actually checking, there is no way of knowing if the drive survived. Had it failed, bigger and cheaper drives are always available.

There are other options too, such as cloud storage. If you have space on your cloud storage plan, do check out how big your archives actually are. For content like scanned family albums, there’s a good chance a service dedicated to just photos or home videos will host them at genuinely competitive rates. You may choose to self-host the photos as well, but there’s no reason not to take advantage of a remote location for the 3-2-1 backup rule.