In the past it was possible to use setxkbdmap dvorak .... This no longer works.
There seems to be no local man page [edit: yes there is; I must have been mistyping]; tldr doesn’t know anything; zsh-completion seems to be giving me plausible suggestions, but they do not contain anything resembling ‘dvorak’.
How can setxkbdmap be used to switch to a Dvorak layout in NixOS 23.11?
Interesting - services.xserver.xkb.layout’s documentation mentions that it can be a comma separated list, but the documentation of services.xserver.xkb.variant doesn’t mention anything about commas, nor does it say that if you do supply a comma-separated list, that it will be matched up with an expected comma separated list in the layout option. But it does seem to work, so thanks for that