@Tereza
What an amazing coincidence!
I've just conducted a session in Microsoft 365 Virtual Summit Madrid this very morning on how to consolidate data with Power Automate, the session has been uploaded in Youtube but unfortunately it is in Spanish.
Anyway, my suggestion is to folllow a totally different approach:
1.- Build a Task Owner dictionaire. So, you can add a 'Select' action block and assign 'Get items' output as its input. THen flip to text mode and assing 'Task Owner' email from dynamic menu.
2.- Next, initialize a variable, let's call it myDictionaryArray, type array, value the expression you will see in this screenshot (it is from the session I run this morning). THis way you will ensure unique values in your array

3.- Once done, remove 'Get items' output and assign 'Filter Array' output as 'Select' input instead
4.- Now, add an 'Apply to each' rename it as 'Apply to each TaskOwner', assign as its input variable 'myDictionaryArray'
5.- Inside the 'Apply to each' you should add a 'Filter Array', rename it as 'Filter Array tasks', assign as its input 'Get items' output and declare a condition rule to get the tasks whose Task Owner email matches with the following expression
items('Apply_to_each_TaskOwner')
6.- Next, still inside 'Apply to each' remove 'Get items' output and assign your first 'Filter Array' output as 'Filter Array tasks' input instead
7.- Now, still inside 'Apply to each' add a 'Create HTML table', assign as its input 'GEt items' output, change the Columns input from default to 'customized', select whatever SP list column you want to show
8.- Next, still inside 'Apply to each' remove 'Get items' output and assign your 'Filter Array Tasks' output as 'Create HTML table' input instead
9.- Finally, still inside 'Apply to each', add a 'Send an email', add 'Create HTML output' in the body (flip to HTML view first) and assign as its destination the following expression:
items('Apply_to_each_TaskOwner')
Hope this makes sense