So
I am looking to do some SPI stuff today
I don't find anything obviously related to SPI, UARTs or serial in the Amaranth language guide, stdlib guide or hardware support section, but I know not everything is documented

Is there a keyword I should be looking for, or a known tutorial/sample code with an example of, showing the interface to interacting with SPI in amaranth?

Context: I have a board definition file from charlotte, with SPI pins here:
https://github.com/mcclure/amaranth-project/blob/main/src/doppler.py#L28
Previously, to make the button work and as recommended by Whitequark, I changed some of the SB_LVCMOS -es up to top to SB_LVCMOS33 -es. I didn't change any of the other and that might not have done anything (I also added PULLUP=1).
Schematic from board's upstream project:
https://github.com/dadamachines/doppler/blob/master/hardware/dadamachnes-doppler-schematic.pdf
Sample SPI code from board's upstream project: 
https://github.com/dadamachines/doppler-FPGA-firmware/blob/master/doppler_simple_io/doppler_simple_io.v#L74