I'd recommend PeerTube for that.

Hey, I was wondering also a while back and remembered that I saved a response from asking ChatGPT..

"how can i easily post a video on a lemmy instance without resorting to youtube."

To post a video on a Lemmy instance without resorting to YouTube or similar platforms, you can follow these steps based on the information gathered from the sources:

Step-by-Step Guide

1. Prepare Your Video: Ensure your video is in a web-friendly format such as WEBM, which is mentioned as a viable option for embedding directly in posts 

2. Upload to a File Hosting Service: Since direct video posting on Lemmy is not widely supported due to storage and bandwidth constraints, upload your video to a file hosting service. Catbox.moe was specifically mentioned as a suitable option for this purpose.

Other alternatives could include ImgBB, Dropbox, or Google Drive, depending on the file size and the hosting service's policies regarding direct linking.

3. Get the Direct Link to Your Video: After uploading, obtain the direct URL to your video file. This is crucial for embedding the video in your Lemmy post.

4. Post on Lemmy: Create a new post on your desired Lemmy instance. Instead of attaching the video file directly, paste the direct URL to your video file in the body of your post. Mention that it's a video and encourage readers to click the link to view it.

Alternative Solutions: As a workaround, it's recommended to upload your video to a separate service designed for video hosting, such as PeerTube or Pixelfed, and then share the link on Lemmy. This approach helps manage the load on Lemmy instances and ensures that video content remains accessible without overburdening the system

Hope this may help.