Odd, it's there in 102.14.0esr on x86_84 (I don't run FF on Pis myself), even without any DRM libs installed. Maybe try entering "DRM" in the search box at the top right? The way the settings page is laid out so sparsely makes it easy to accidentally skip past things.
There's also a current thread named "Background on Firefox setting Digital Rights Management (DRM) Content with Google Widevine" in alt.comp.software.firefox which might mention some information that's of interest to you.
Firefox's ESR releases support what the major releases that they're based on support, so 102 ESR should be fine.