Non-UK users can get a standard mastercard. It’s the only thing they let me order. I want a Visa because I’m going to Spain soon and some ATMs are cheaper in Spain with the Visa card.
UK banks actually used to issue Maestro about a decade ago but switched to issuing visas instead due to the better consumer protection that they offered at the time. I think this was before the mastercard charge back scheme.
I’m also relatively sure that at least in the UK, Maestro is still accepted at most if not all merchants, partially because we used to issue them and we’ve just never gotten rid of the technology and partly because we’re quite close to Germany/Austria/Netherlands etc