Connecting Samsung T7 to iPhone iOS 15 via Lightning to USB3 camera adapter

This question is more about documenting how I was able to connect my external SSD to my iPhone 13 Pro on iOS 15 since I had some trouble getting it to be recognized in the Files app.

Setup

I have a 2TB Samsung T7 that I'm connecting to my phone via the Lightning to USB3 camera adapter. I have it plugged into my phone, the port is powered, and the SSD is plugged into the USB-A port. The light on the SSD is slowly blinking blue (~every 5s), but when I open the Files app, no drives are recognized. The T7 has two partitions, one formatted as an encrypted APFS partition, the other as an unencrypted APFS partition. The SSD uses a GUID partition map scheme.

The SSD would connect to my 2018 11" iPad Pro and recognize both partitions immediately. The SSD connects to my laptop that I used to reformat it.

All connectors were the ones that came with the SSD or official Apple cables.

My phone would recognize a 1TB T5 SSD I already had formatted as exFAT the first time I just tried to plug it in.

What seemed to be the problem

I'm not for sure on this, but it appeared that the SSD wasn't being powered enough. I think this was because it was the first time my phone has tried to connect to the device and it wasn't providing enough power since it didn't recognize the SSD. My phone was below 80% power and I was charging with 12W+ power supplies.

What seemed to solve the problem

Two things happened around the same time, I'm not sure which made my phone recognize the SSD:

1. Adding a third exFAT, very small partition on to the SSD. This might have solved it because it's a more common file system to find on external storage, maybe there were connection issue when there were only APFS partitions. After deleting the exFAT partition, the device was still recognized.
2. My phone charged to over 80% and enough power was being diverted to the SSD.

I think the solution was having an exFAT partition for the first connection though.

After first connection, I checked that I could read APFS copy-on-write clones from the SSD and could write an 8 GB movie from the phone to the SSD successfully. I could watch 4K60fps HDR videos in real time from the SSD. The file transfer ended up taking ~10min -> 100Mbps write speed.