Transfer custom ringtones to iPhone using a computer running Linux

I received an iPhone 7 from my employer. I am traditionally an Android user and have never used iPhone before. I have Linux running on my PCs at home. How can transfer ringtones from PC to iPhone easily? I have read scattered posts about this, but most people seem to be doing this via Windows or macOS. I am using Linux Mint. I have Audacity installed on my Linux computer, and I am quite comfortable working with audio files.