This can e.g. be seen in https://github.com/r-spatial/qgisprocess/actions/runs/7259352022/job/19776322636#step:22:45.
It was found that these warnings disappear if test-compat-raster.R is removed; this file is run before test-compat-terra.R, so an interplay between {raster} and {terra} is at stake.
This could be reduced to the following finding. On Ubuntu, it appears that if raster::raster() has been called, subsequently writing a SpatVector object to a GeoPackage with terra::writeVector() emits the warning.
Reported at rspatial/terra#1377.