Use AirDrop to send multiple photos at once
Create a shared iCloud Photos album and add the photos
Use iCloud Drive or Files to upload the photos, then share the folder link
Email the photos in batches if the total size is small
Use a cloud service like Google Photos, Dropbox, or OneDrive and share the album or folder
Connect the iPhone to a computer and sync photos through Finder or iTunes
Use Messages or WhatsApp to send selected photos in groups
Use a photo transfer app that supports bulk sharing to iPhone
Save the photos to a ZIP file and send the ZIP if the recipient can unzip it on iPhone
Use a USB drive with Lightning or USB-C support and copy the photos to the iPhone