Here is few software tools that you can use for online teaching. If you use different software please share with others in comment section. 😍
You may need separate screen sharing software when using these like Zoom, Skype, OBS etc.
OpenBoard is an open source cross-platform teaching software for interactive whiteboard designed primarily for use in schools and universities.

Microsoft Whiteboard is freely available on Microsoft Store.
Sytem Requirements: Windows 10 version 14393.0 or higher

SketchBook has a gorgeous interface that maximizes the drawing space of every device. Because of that reason it can use as a whiteboard software for online teaching.

Very informative😍. We can use Microsoft One Note Also.