Leica's long partnership with Huawei has always been very institutional. The companies would collaborate on two phone lines yearly, share knowledge, and announce well-polished and finished products. 
As a consequence of Huawei's geopolitical tribulations, Leica moved on and partnered with Xiaomi. Two months in, we already see things that Huawei would have never dared to reveal. 

In July, Xiaomi unveiled the 12S Ultra, a behemoth of a smartphone with a gigantic rear camera module that screams "photography" at the top of its virtual lungs. Now, it's pushing the envelope even further with the Xiaomi 12S Ultra Concept, a not-for-sale phone with a 50MP 1" sensor and a — wait for it — a ring adapter for Leica M-series lenses. 

The company produced ten physical units of the concept, sending them to Chinese influencers to test and share on social networks. It also shared sample pictures taken with the phone. They are indeed impressive and show levels of natural bokeh and depth of field blur that computational photography still hasn't been able to match.

According to Engadget, each unit cost about $40,000 to produce, and they were all developed alongside the commercially available version of the Xiaomi 12S Ultra. Given the insane price tag and its niche appeal, we doubt Xiaomi will ever bring an M-mount smartphone to the market. Nonetheless, it's interesting to see how the company is leveraging its collaboration with Leica, pushing the German brand to participate in marketing stunts that are both off-brand and refreshingly cool. 

It's not the first time a smartphone producer has attempted this feat. In 2014, Sony released the QX1 and QX30, two smartphone add-ons that would let users mount the company's E-Lenses on their Xperia phones. In that case, lenses weren't mounted directly on the phone, though, and images captured by the two add-ons were sent to the smartphone wirelessly after being captured by the additional sensors.