> Security is the main concern.
> Tool should be web based.
From your question it kinda sounds you actually have 3 main concerns, not just security. I can't give you any suggestions for web based tools but I can suggest:
1. Obtain a public SSH key out-of-band with the party that needs the large file and give them access to an SFTP share with that key.
2. Upload the file to a private S3 bucket and send them a signed link[1]
[1] https://docs.aws.amazon.com/AmazonS3/latest/userguide/ShareO...
If you're hosting in the cloud, you can improve the security posture using confidential computing like AWS Nitro Enclaves. Contact me at bobbie.chen@anjuna.io if you'd like more info on getting started with that.
For non-technical partners, we have a simple instructional document on how to download and use Filezilla[1] to connect. We haven't had many challenges.