Sharepoint Online 2019 simple one to many webpart?

[Jamie Marshall]

How do you display a many to one list based on what is selected in a parent list one SharePoint Online 2019?

Here is a video that shows how to do what I'm looking for in classic:

https://www.youtube.com/watch?v=gqHvAZyvX9k

I feel like this is such a simple ask, but I can't find for the life of me how to do such a simple thing.  I've already been through all the basic docs here:

https://support.office.com/en-us/article/connect-web-parts-in-sharepoint-online-b457668c-d843-4b1b-8...

https://support.office.com/en-us/article/use-the-list-web-part-ef0a1b80-f8b3-443d-b04a-1e76c70b5537

[#2]

I might be wrong but what happens in SP 2019 is that WebPart connections in OOB WebParts are not available and I have not checked if you can have this support with custom SPFx WebParts on SP 2019 assuming you can have latest versions of SPFx there (I'm talking here about dynamic data)