HEIF import on Windows LRC was working v11. After upgrade to 12.1 LRC does't even see the files.
Apparently, unless your source is an iPhone, you are out of luck.
Now, if you are using an iPhone, and support went away, that is different. So what camera?
One point, it appears many cameras will store the HEIF or HEIC file with a file extension, HIF for example. If you copy those files via a SD card reader, then the OS may not understand that they are HEIF files, you would need to rename them as to have the complete file extension, But, on some cameras, if you copy the files via a USB cable between computer and camera, the on cameras board processor will make that change for you.
Android HEIF/HEVC images are now supported, as well as iOS:
Please provide more details about your issue: Which camera is producing them? Are you importing via a USB cable or a card reader? At what step does LR "doesn't even see the files"?
I'm using an iPhone 12 pro that automatically sends the HEIF files to icloud. I use a Mac mini to export originals from Apple iCloud to a usb external disk on my network. I open LRC 12.1 on my windows 1 laptop and use the import menu item on the USB directory. I have deleted all the "." files created by Mac OS. The LRC import screen shows the photos to be imported but not the MOV files which most are (preview unavailable for this file). Selecting all and clicking the IMPORT button produces the attached error file. This is the same process I have done hundreds of times with the earlier version of LRC. The fact the LRC was updated 5 days ago makes me suspicious. Thanks
Failed to find a place for the imported file. (1) X:\iCloud Downloads\221213-221225\IMG_3502.HEIC The folder(s) could not be found. (260) X:\iCloud Downloads\221213-221225\IMG_3456.HEIC ...
These errors suggest that LR is having trouble accessing the X drive. Is the X the external drive you're importing from or the drive you're importing to?
As a first step, if you're importing from X, try copying several of the photos from to your Desktop, and importing into LR from the Desktop. Do you get any errors?
If you're importing to X, try importing to a test folder on your Desktop instead. Do you get any errors?
I moved the photos from the X drive to a local disk to do the import and it fixed the problem. Thanks for your help.