iMazing can save your iPhone/iPad backups to an external drive, relieving the necessity of saving them to the internal drive..
I use iMazing. It works great but you do need to read the guides to properly set up external backups.
iMazing saved my Calendar from destruction when for some reason Catalina wouldn't sync my iPhone Calendar. After recovering my Calendar and eventually replacing my iMac and moving to macOS Monterey & Sonoma it's working again but I still use iMazing for backups. It has also enabled me to easily export Calendar, Contacts, Photos, Messages and more.
FWIW, I would not suggest using the symlink method as described earlier. It may or may not work and even if it works now it may not after some future macOS update or upgrade. I have had no success using symlinks to/from locations in ~/Library folders on macOS subsequent to Catalina.