\ValueFormatters\FormatterOptions is a very generic Object that allegedly used to be used with a lot of options, but might now be used with only a few, among which: ValueFormatter::OPT_LANG = 'lang' and FormatterLabelDescriptionLookupFactory::OPT_LANGUAGE_FALLBACK_CHAIN = 'languages'. Since it is so very generic, it is hard for IDE's to give good coding assistance. It would be useful to understand better with which keys it is actually used.
That knowledge could help us decide whether we can switch to some more strongly typed variant of it or if we can drop it in parts of our code in favor of passing the expected options explicitly.

This investigation is in particular intended to help with understanding the usage of \Wikibase\Lib\LanguageFallbackChain. This is could be relevant for T250930, T247057 and T256405.

This likely needs additional looking into the following Extensions:

• Math
• MathSearch
• Score
• WikibaseMediaInfo
• Lexeme
• WikibaseQualityConstraints
• Maps
• some more?