Created attachment 144975 [details]
Example slide PPTX
Open attached example slide PPTX that comes from Bug 50265 slide 3.
See that red text in legend appears missing.
Note: Text is there and can be seen if legend box size is increased in LO.
Can't say if it's about box size or Microsoft fonts rendering.
Repro from LO 3.4.0 to 6.2+. In Lo 3.3 it was show but with wrong shape.
Created attachment 144976 [details]
Example slide PDF from MSO
confirm in LO 188.8.131.52 on Windows 10
Text Box is "Do not Autofit" like in Bug 116418. But I will not mark duplicate because it's a legend.