Just following up with a belated thanks to chewitt and VLouis — with your help, I was able to do this.
I made a slightly modified version of Estuary that displays available subtitles for each film, as you are browsing (e.g., on the Recently Added page). The mod is simple: brief edits to two files in the skin.
In case anybody else wants to try, here are the steps, using EstuPlus as the name of the new skin:
1. copy the contents of /usr/share/kodi/addons/skin.estuary/ to /storage/.kodi/addons/skin.estuPlus
This clones the Estuary skin, which will be slightly modified to become the EstuPlus skin.
2. Edit /storage/.kodi/addons/skin.estuPlus/addon.xml, changing only the <addon> element, e.g.:
<addon id="skin.estuPlus" version="4.0.0" name="EstuPlus" provider-name="mrob42">
3. Edit /storage/.kodi/addons/skin.estuPlus/xml/Includes.xml, as follows:
Inside this file, search for the string ListItem.Duration, and identify the <control> element that invokes it. Each <control> element shows a small box on the bottom of the display.
Following the closing tag of the ListItem.Duration control (i.e., </control>), add the following lines:
QuoteDisplay More<!-- EstuPlus START 08-31-2025 -->
<control type="group">
<width>115</width>
<visible>!String.IsEmpty(ListItem.Property(SubtitleLanguage.1))</visible>
<control type="label">
<width>115</width>
<height>60</height>
<align>center</align>
<aligny>center</aligny>
<label>[UPPERCASE]$INFO[ListItem.Property(SubtitleLanguage.1)][/UPPERCASE]</label>
<font>font_flag</font>
</control>
<include content="MediaFlag">
<param name="texture" value="flags/flag.png" />
</include>
</control>
<!-- EstuPlus END 08-31-2025 -->
If you want to display the first three subtitle languages available, add two more identical <control> elements following this one, but displaying SubtitleLanguage.2 and SubtitleLanguage.3.
4. Reboot Kodi, navigate to Add-Ons, enable the EstuPlus add-on, and choose it via Interface > Skin > EstuPlus.
5. Just in case, make a back-up copy of /storage/.kodi/addons/skin.estuPlus