It is 2019, and it is quite surprising - and disappointing - that we STILL haven't universally solved the means to easily, securely, and (yes, I'll use this term again) universally share files. I wish we could share files in a peer-to-peer fashion securely without hindrance of mobile platform, nor blockage of network MiTM, etc.
Rather than the google solution suggested by a sibling comment, I’d suggest a look at send.firefox.com.
If you're somewhere with poor (or no) network connectivity you can still use Google Files or AirDrop (I believe, not 100% sure on AirDrop).