Bought myself an Ampere Altra system

Armv8.6-A is almost the same as Armv9.1-A, except that a few features are not mandatory.

There have been no consumer chips with Armv9.1-A, but only with Armv9.0-A and with Armv9.2-A. The only CPU with Armv8.6-A that has ever been announced publicly was the now obsolete Neoverse N2. Neoverse N2 has been skipped by Amazon and I do not know if any other major cloud vendor has used it.

So what you really search for are CPUs with Armv9.2-A (i.e. a superset of Armv8.6-A), i.e. with Cortex-A520 or Cortex-A720 or Cortex-X4 or Cortex-A725 or Cortex-X925.

There are many smartphones launched last year or this year with these CPU cores, but except for them the list of choices is short, i.e. either the very cheap Radxa Orion O6 (Cortex-A720 based), which is fine, but its software is immature, or a very expensive NVIDIA DGX development system (Cortex-X925 based; $4000 from NVIDIA or $3000 from ASUS), or one of the latest Apple computers, which support Armv8.7-A (which do not have SVE, but which have SME).

For the latest Qualcomm CPUs, I have no idea what ISA is supported by them, because Qualcomm always hides very deeply any technical information about their products.

If all you care about is the CPU, then a mid-range Android smartphone in the $400-$500 price range could be a better development system, especially if its USB Type C connector supports USB 3.0 and DisplayPort, like some Motorola Edge models, allowing you to use an external monitor and a docking station.

If you also care about testing together with some standard desktop/server peripherals, the mini-ITX motherboard of Radxa Orion O6 is more appropriate, but encountering bugs in some of its Linux device drivers is likely, which may slow down the development until they are handled.