I used Puffin on my phone with no problems, throw-away gmail address, fake name.
Also worked a previous time using Vivaldi and Nada email address.
Just tried it now with another throw-away email, worked fine, (2 mins before deal expired).
What had to be allowed:[FREE] Packt Book of the Day
And TBH, didn't read any reviews, was more like: ooooo->Powershell->*FREE*->MINE!!!!
BTW, thinking about the sign up process, all three times I've done it I've had no ReCaptcha to play with:Fill in details + Submit = access immediately
(No ReCaptcha, no email verification, nothing)
And that's with uBlock Origin, uMatrix, Cookie AutoDelete, and a Hosts file that's ~500kB full of ad/analytics/malware/etc blocked domains.