A user who bought his iPhone 12 was using it with his Circles.Life line and detected that he was connected in 5G (M1 NSA network) at Orchard area (near Shaw centre). The signal bar shows full bars of 5G. He ran speedtest and it scored 242 Mbps downlink and 35.1 Mbps for uplink.
It looks like Circles.Life should be the first MVNO in Singapore (running on M1) to support 5G, bringing 5G at lower cost to the masses. Other telcos are charging a ridiculous subscription fee.
In some countries, telcos are giving away free trial 5G SIMs with gigabyte of data for end users to test it out. e.g. Fareastone in Taiwan.
Here is a screen shot of the 5G speedtest on the iPhone 12 with Circles.Life $28 plan (existing 4G sim card).