Flipgrid, pretty easy to set up. They can record live or upload a video.
Google Classroom. Upload the file here.
MS Teams. My school is pushing Teams hard, so I started asking students to send me a chat message in Teams and attach the video. If they're on their phone it's exactly like adding a video to a text message. I liked Flipgrid the best, but used Teams the most because I wanted to learn the program better.