A technical note: OpenType Layout does have a way of representing the appropriate _cursor positions_ to use for components of a ligature[1], which is a good proxy for where the individual glyph boundaries are in the trivial case (fi and fl, say) but these tables are not reliably included in all fonts, and they are not actually used by much client software (last I checked they were used by CoreText but not by HarfBuzz or DirectWrite.)
[1]: https://learn.microsoft.com/en-us/typography/opentype/spec/g...