For things smaller than around 10gb, I tend to use S3. Either with pre-signed links behind a little bespoke portal that people can log into and see what files

For things smaller than around 10gb, I tend to use S3. Either with pre-signed links behind a little bespoke portal that people can log into and see what files I've "shared" with them, or just direct S3 links for those that what to automate it all. For bigger things, there are two basic paths: If it's to someone that's not primary a tech person, then the data goes on a portable hard drive, and I either drive it to them, or mail it and walk them through accessing the data. In both cases I encrypt the data, generally with Veracrypt. If it's to someone that won't mind using AWS's toolchain, and has decent connectivity, I'll use Snowcone or Snowball to get the data to S3 and give them S3 URLs. I tend to get the data to S3 sooner or later so I can migrate it to Glacier. More than once I've had to recover GBs or TBs of data because the customer lost it, so I'm prepared now.