The problem is that a cassette that starts with a smallest cog of 11t is not good for small wheel bikes, the gear inch it gives with a usual 52 or 53t chainring and 52/53x11 is too short and the big cogs above 42 are completely useless. Using very big 60t or more chainring is not a good solution because they aren't standard and do not fit on many folding bikes.

This is the reason why bike manufacturers like Moulton, Riese & Müller and others use special cassettes with a smallest cog of 10t or 9t.

Shimano has only one solution that accept a 10t cog, its the latest MTB 12s Hyperglide+ which is only compatible with Shimano microspline hub and only in 10-45 or 10-51 (or even bigger from third party).

Shimano had the Capreo drivetrain specially made for small wheels bike but its obsolete (cassette is max 9-28) and anyway discontinued from Shimano and n spare parts available anymore.

Therefore the choice of SRAM XD or XDR rear hub that accepts cassettes starting with a 9t cog, for which there are several cassettes options that fits very well for small wheel bikes with a wide enough gear inch range to avoid the need of a double chainring and that in 11s are compatible with SRAM, Shimano and even Campagnolo derailleurs.

The picture I put of my Birdy show such a solution : XDR rear hub, 11s 9-34t 378% range cassette and Ultegra RD-R8000-GS medium cage rear derailleur (and for a frame that accepts it, there is also a 9-39t cassette 11s for XD/XDR rear hub usuable with a Shimano GRX derailleur).