Why Did My Photo Captions Disappear After Takeout?
Captions you typed in Google Photos are in the .json files, not in the pictures. Here is where to find them and how to keep them.
They are not lost. Open any .json sidecar and look for the description field: that is your caption, exactly as you typed it.
Like the dates, captions lived in Google's database rather than inside your images. Google exported them to the sidecar and left the photo alone. No normal photo viewer reads those sidecars, so your captions look like they vanished. There is a proper place for a caption inside an image file, in EXIF and IPTC, and that is where it needs to go if it is going to survive.
This matters more than it sounds. Dates you can often recover from other clues. A caption is something you wrote, and if you delete the .json files before copying it out, it is gone permanently.
So do not delete the sidecars until the information is inside your photos. The app reads each one and writes the date, the GPS and the description into the image itself, so your captions come with you into Apple Photos, Immich, digiKam or whatever you move to next. Merge first, check a few, then clear the .json files. The first 500 photos are free.