OpenType preview in Text and Font Dialog does not seem to work

Steps to reproduce:

• Type some text set to a font with OT features
  • I'm using IBM Plex Sans
• Open Text and Font side panel
• Click on the Features tab

What happened?

It only shows the default on the panel.

e.g.

• You don't see a slashed zero beside the Slashed Zero checkbox
• ss02 is supposed to change the g style to single-story; that's not shown

What should have happened?

I believe it's supposed to show how the character will appear if you select the OT feature

Inkscape Version and Operating System:

• Inkscape Version: 1.0beta2 (2b71d25, 2019-12-03) and 1.0beta2 (9d7bad2, 2020-03-08)
• Operating System: macOS
• Operating System version: 10.15.4