It is more convenient to develop on the LPC55S69-EVK as it has PIO0_5, the ISP0 pin, exposed. This allows forcing boot-to-bootloader, so you can't realy brick yourself until you start playing with secure boot settings. Also of course, it has the debugger embedded, vs. having to somehow attach it to the Solo V2's Tag-Connect headers. However, there is no NFC on the dev kit, two buttons instead of three, and the RGB led doesn't work properly.

There is also some low-effort support for the (cheap!) OKdo E1. This board however does not have a crystal soldered by default, and hence cannot run the USB HS peripheral. This also means it has one less bidirectional USB endpoint; keep this in mind when USB classes stop working. It can be selected via the board-okdoe1, which patches the board-lpcxpresso55 implementation.

For development, on the main boards, we recommend using Segger's JLinkGDBServer:

JLinkGDBServer -strict -device LPC55S69 -if SWD -vd

For OKdo E1, there's no JLink support, modify .cargo/config in the runner to use pyocd.gdb, and try your luck with

pyocd gdbserver

Flashing firmware is much slower.