While joint accounts aren’t available yet, as a workaround you could pop in to your local Wilko store and buy a generic Revolut VISA card for less than £5 and add it to your account. All additional cards use the same currency balances available within your Revolut account.
These generic VISA card do not have any name embossed on them - they just have a long card number and expiration date. But it does have a unique PIN which can be changed at most ATMs here in the UK.
You are allowed to install the Revolut on multiple devices.