Or any other file sharing website for that matter, but at least use something more secure from a more trustworthy company, such as https://send.firefox.com/ (never heard of sendgb.com).

Yes firefox is good option. Sendgb is from Estonia. Sendgb allows file transfer up to 5 GB. File are storages up to 90 days for free. Nobody knows which one is more safety. Sometimes big services have more security problems...like Dropbox, wetransfer etc...

Firefox Send is E2EE (albeit via JS code served at every connection), contrary to sendgb (AFAICT), which makes it a strictly better option.