Thanks to enabling HEIC files in Lightroom Classic’s Windows version, I have been able to re-sync the vast majority of HEIC images from iCloud photo import with the iOS mobile app.
Nevertheless, almost all HEIC files from June and Juli of last year strangely have sync issues on the desktop and Web, but are shown correctly on the mobile app.
I have tried to resolve this reverting all changes to those images, but without any success.
Additionally, the original versions from images, taken as HEIC, even when those images were converted to JPEG can be extracted from the Mac iCloud photos app. These original HEIC images cannot be imported into the desktop version from Lightroom.
Thanks, Laura, good point, will do!