What is the bug or the crash?

GetMap WMS request to QGIS server shows image with features shifted by few meters comparing to map that is shown in QGIS Desktop when I open the same QGS file.

The QGS file contains two vector layers, layer vaclav-epsg-3857 with four points in EPSG:3857 (green crosses) and layer vaclav-epsg-5514 with the same four points in EPSG:5514 (red circles). The project's CRS is EPSG:3857. One of suggested datum transformations is used:

If I open the QGS file in QGIS Desktop v3.40.2, I see points from both layers placed in the same location:

However, if I publish the same QGS file to QGIS Server v3.40.2 and send WMS GetMap request, e.g.

http://localhost:8090/qgis/?MAP=/qgis/data/vaclav.qgs&SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&BBOX=1606261.367126520025%2C6460065.113021261059%2C1606371.941027208464%2C6460150.805113065057&CRS=EPSG%3A3857&WIDTH=1032&HEIGHT=799&LAYERS=OpenStreetMap,vaclav-epsg-3857,vaclav-epsg-5514&STYLES=&FORMAT=image%2Fpng&DPI=96&MAP_RESOLUTION=96&FORMAT_OPTIONS=dpi%3A96&TRANSPARENT=TRUE

four points in vaclav-epsg-5514 layer (red circles) are shifted by several meters:

I expect that points in GetMap request should be in the same location as they are in QGIS Desktop. I guess it's because QGIS Server somehow ignores the selected datum transformation.

I did not find similar bug among open issues. However I found this StackExchange post from 2020 that suggests that the same issue was also with QGIS 3.10: https://gis.stackexchange.com/questions/364744/datum-transformation-in-qgis-server-3-10

Steps to reproduce the issue

1. Download and unzip file data.zip
2. Open vaclav.qgs in QGIS Desktop. You should see four green crosses and four red circles from placed in the same locations:

3. Publish the same QGS file to QGIS Server. You can use containerized QGIS Server (this is how I am using it).
4. Send WMS GetMap request, e.g.

http://localhost:8090/qgis/?MAP=/qgis/data/vaclav.qgs&SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&BBOX=1606261.367126520025%2C6460065.113021261059%2C1606371.941027208464%2C6460150.805113065057&CRS=EPSG%3A3857&WIDTH=1032&HEIGHT=799&LAYERS=OpenStreetMap,vaclav-epsg-3857,vaclav-epsg-5514&STYLES=&FORMAT=image%2Fpng&DPI=96&MAP_RESOLUTION=96&FORMAT_OPTIONS=dpi%3A96&TRANSPARENT=TRUE

(you probably need to adjust MAP parameter value to correct path).
5. See the error, four points in vaclav-epsg-5514 layer (red circles) are shifted by several meters:

Versions

All QGS file, QGIS Desktop and QGIS Server are v3.40.2. This StackExchange post from 2020 suggests that the issue was also with QGIS 3.10, so maybe it's quite old: https://gis.stackexchange.com/questions/364744/datum-transformation-in-qgis-server-3-10

Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

Additional context

No response