Have encountered the same after updating Android Studio to Arctic Fox 2020.3.1 (and now the Bumblebee 2021.1.1).

Decide not to wait anymore, did some search and found that this is happened because the latest version of Markdown by JetBrains requires Java Chromium Embedded Framework (JCEF), but it is not bundled with the default runtime for the IDE.

Update the runtime to the one with JCEF in the following steps could solve this issue:

Select Help > Find Action from the Android Studio menu.
Enter "Choose Boot Java Runtime for the IDE" and select it from the suggestion list.
Select the runtime that comes with JCEF support as shown in the image below: enter image description here
Click OK and restart the IDE.
Disclaimer Apply the change at your own risk since there is a statement claiming that changing the runtime may cause unexpected problems. Will again update this post if I have encountered any other issues after this has been set.

Update: Joachim Schuster has written a detailed article to explain on this and the steps to fix it.