The startup got a European banking licence in late 2018
It appears to have been rather quiet about it since and has allegedly withdrawn a licence application in Luxembourg.
Not that a European licence may be of much use in he UK in a year's time, if N26 is any guide
Revolut's web footer says in small print:
Revolut Ltd (No. 08804411) is authorised by the Financial Conduct Authority under the Electronic Money Regulations 2011.
The word "bank" is also notably absent from their publicity material. It's not so much a mobile banking app as a means of managing your fractional interest in an account in Revolut's name at a real bank. That may change over time, but it doesn't seem like it has yet.