It seems the preparations for HTML production broke the template handling for out-of-source installs (the real installs) - please fix.
Either kindly roll back the HTML implementation or make it work, please.
Another cause can be the change to pure pyproject.toml based packaging and removal of setup.py from the build process. Suggest to start from the change set at https://git.sr.ht/~sthagen/liitos/commit/041e015f5decd061e657d5fa3a3709673a3b0a5b
Fixed in release 2022.1.11