Created attachment 164812 [details]
This pptx [originally MSO generated, having Calibri font] has text displayed differently when opened in LO even when substitute fonts [Carlito, since I don't have Calibri] have same metrics. Due to same metrics, it should have been exactly similar, I expected.
See that at the end of one/multiple lines, one/few words either have been pushed to next line or extra words have been included in the line.
I'm uploading this side by side comparison for only few of the slides via gif
Build ID: 8061b3e9204bef6b321a21033174034a5e2ea88e
CPU threads: 4; OS: Linux 5.4; UI render: default; VCL: gtk3
Locale: en-IN (en_IN); UI: en-US
more details in discussion at https://ask.libreoffice.org/en/question/261699/powerpoint-compatibility-text-not-displayed-identically-even-when-substitute-fonts-have-same-metrics/
Created attachment 164813 [details]
Created attachment 169719 [details]
PDF exported in PowerPoint
This isn't a matter of substituting font, even on the same system with the same fonts the text layout in text boxes is different.
Created attachment 169720 [details]
PDF exported in LO 18.104.22.168 (w Calibri)
Created attachment 169721 [details]
PPT saved in PP
What's interesting is that the PPT of the same presentation is shown almost perfectly identical, except the title on slide 3 (and a small issue on slide 5).