Blockly is JavaScript library that runs App Inventor's code-blocks editor. And the 2021 Blockly Developer Summit has just been opened for registration The summit is a chance for people who use Blockly (eg open-source contributors to App Inventor) to learn about the direction of the library, and what people are doing with it.
If you're interested in learning more about Blockly (eg, possible GSoC contributors) this year the summit will be held virtually over two days, Wednesday April 28th and Thursday April 29th. Each day will have two sessions, a morning session from 9-11 AM PT, and an evening session from 6-8 PM PT. All of the talks for the summit will be pre-recorded, and are intended to be watched before the summit. That way there will be plenty of time during the sessions for Q&A, and learning about other peoples' projects =)
For more details you can refer to the announcement post on the blockly email list.
To register you just have to fill out this short registration form. Registration is totally free! I believe it's only required so that they can send you the link to the live session via email (rather than posting it publicly).
App Inventor and Blockly have an interesting related history, so I can't wait to see some of you guys there to continue that =)
Best,
Beka