I recall your out-of-storage woes; I was experiencing similar issues. After I did the latest iPhone iOS update however, I GAINED back 3 GB (yes, gigabytes) of free space on the phone. I have read elsewhere of others reporting this 3 GB number. I was doing this on an iPhone 6, so maybe that's the difference.
On a Mac since 1984. Currently: 24" M1 iMac, M2 Pro Mac mini with 27" BenQ monitor, M2 Macbook Air, MacOS 14.x; iPhones, iPods (yes, still) and iPads.