Filtering does not work for fields with Value relation with Multiple selections

[alex-cit]

Description
Single select and Multi select filters do not work on fields that use Value relations widget with the option "Allow multiple selections" (when there are multiple values stored in a field). While it is possible to set up filter for such field in QGIS and use it in the mobile app, the result of filtering is always 0 features.

Environment
Production

Application (+ app version, build, operating system)
v2026.2.0, Android

Steps to reproduce

1. Set up a Single select or Multi select Filter in QGIS for a field that is configured with Value relation with enabled multiple selections.
2. In the mobile app, try filtering features using one or multiple values from the list.

Actual results
There are 0 features that match the filter - all features from the layer disappears from the map.

Expected results
Depends on the intented use of filters:

• If the Single and Multi select filter is not appropriate for Value relation+multiple selection, the field should not be offered when setting up the filter in QGIS
• If it should work also for mutiple selection fields, the app should display the appropriate result of the filter. Note that there are (at least) two options for multiselect logic: OR vs. AND.

[alex-cit]

It also appears there is an UI issue for the combination of multi select filter and field with value relation+multiple selections. The active filter displays "XX selected values". When it is reopened, the current selection is not highlighted. After selecting some values again, the filter adds the number to the message to the "XY selected values" instead of replacing the number by current selection (leading to, say, 16 selected values in a list of 5 options)

Screen_Recording_20260427_140425.mp4

This does not happen in case of multi select filter with another type of field. Here, the filter displays values and the message correctly.

[Withalion]

Hello @alex-cit, thank you for reporting this issue. We will look into it