No need to rely on app-specific configs. You can disable it globally in your fontconfig. For example, this disables ligatures in the Cascadia Code font:
<match target="font">
<test name="family" compare="eq" ignore-blanks="true">
<string>Cascadia Code</string>
</test>
<edit name="fontfeatures" mode="append">
<string>liga off</string>
<string>dlig off</string>
</edit>
</match>
Here is someone disabling ligatures for Noto Sans Mono:
https://blahg.josefsipek.net/?p=610