I learned this hard way (ok not hard way, I had balance of 2 USD at that time) when Revolut locked me out. They simply stopped releasing new version of their app for Android version I had. Day by day I lost access to my money.

I simply got error that I can't log in and I should update an app but there was not any update.

Took me two days to get to their support (I don't know how it is now, but at that time all ways was directing me to use support option in app which was not functioning). And support told me if I want to get my 2 USD I should buy a new phone.

2 USD is nothing to continue the fight but I've understood I don't want to give any money to such operator. I am not Revolut user for more than 6 years now.