Apple is sending out an update to all its old iPhones — including the really old ones — to fix an issue that would definitely affect their use as navigation devices. This issue doesn’t affect newer iPhones which are presumably patched for the issue already.
Starting November 3, 2019, some iPhone and iPad models introduced in 2012 and earlier will require an iOS update to maintain accurate GPS location and keep the correct date and time. This is due to the GPS time rollover issue that began affecting GPS-enabled products from other manufacturers on April 6, 2019. Affected Apple devices are not impacted until November 3, 2019.
Apple will release the updates on November 3rd, with older iPhones receiving it as a patch to their last updated iOS version. Apple is expected to be releasing updates to iPadOS, iOS 13 and macOS Catalina shortly before.