How can I directly backup my phone on an external drive?

fredik ilja wrote:

My Mac has limited storage and I don't want to have pay for additional icloud space. How can I directly backup my phone on an external drive?

you can try something like—

iMazing | iPhone, iPad & iPod Manager for Mac & PC

iMazing is a very good application and it can create & store iPhone backups on any drive.

Just be aware that iMazing's default backup location is the same as the Finder's location for iOS backups (~/Library/MobileSync) and the first time you make a backup with iMazing it requires that you already have a regular Finder-based backup of your iOS device present. So at first you will have 2 complete backups, occupying 2x the space. After that, you can move your iMazing backup location to another drive ... but unfortunately that has not been a straightforward or well documented process. The good news is that the latest iMazing update has made that process easier. Here's the actual text from their announcement yesterday:

"We also added a small addition to the contextual menu (right-click) allowing you to Export Backup and Archives to Another Location, which does exactly what it says! Now with a couple of clicks you can move and preserve the complete archives of your iOS backup, especially handy when you find your original backup location running low on space."

You also need to give iMazing Full Disk Access in System Preferences > Security & Privacy > Privacy.