Side note for anybody coming here...
On Ubuntu, with snapd, the keyboard-setup.serviceoverride.conf create a loop in dependencies.
$ systemd-analyze verify default.target
local-fs.target: Found ordering cycle on snap-chromium-2623.mount/start
local-fs.target: Found dependency on local-fs-pre.target/start
local-fs.target: Found dependency on keyboard-setup.service/start
local-fs.target: Found dependency on systemd-tmpfiles-setup.service/start
local-fs.target: Found dependency on local-fs.target/start
local-fs.target: Job snap-chromium-2623.mount/start deleted to break ordering cycle starting with local-fs.target/start
local-fs.target: Found ordering cycle on local-fs-pre.target/start
local-fs.target: Found dependency on keyboard-setup.service/start
local-fs.target: Found dependency on systemd-tmpfiles-setup.service/start
local-fs.target: Found dependency on local-fs.target/start
local-fs.target: Job local-fs-pre.target/start deleted to break ordering cycle starting with local-fs.target/start
For info only since this is a Debian thread.