I will resume here briefly my experience of July 2022. Three nights in Gibraltar without using any Gibraltar Pounds or British Pounds GBP. Of course you could be more prudent than I've been, but I observe that in my stay I could rely on Euros and debit card only.

If you have Euros cash, you can pay in _some_ places, not everywhere. The exchange rate is going to be possibly bad but, more likely, rough: at the hostel (I had booked  but not finished to pay online) they told me _"100 pounds or 100 euros"_ while on the same day I paid 5 Euros for a pint of beer that was on the list at 3.60 Pounds.

The main credit and debit cards are accepted everywhere even for small amounts: I've then paid by card one coffee, or one orange juice, even a single bottle of water at the supermarket (0.45 GBP = 0.52 Euros on that day). This is not trivial if you come from a country - like mine, Italy - where electronic payments are sitll expensive for those who sell. Instead, in Gibraltar I've seen the same trend I saw in the UK, where paying any small amount by card is ok.

The recommendation is, as usual, to have some amount in the local currency but in Gibraltar it will be fine and funny to make without!