Because it is not a conventional drop-down using the "Set drop-down list value on web page" doesn't work all that well.
You can use a bit of javascript and variables for this.
Hit F12 to show developer tools, you will see there is a list of hidden items with the class class="gug-select-items gug-select-hide"
you will use this in the javascript.

Then add a 'Press button on web page' function and add the 'drop-down' element, which is a <div>

Then edit the element selector and change it to text editor.

then change the selector to make use of the nth-child(0)
selector but use a variable for the index.
so it looks something like #gug-overall-ranking-select > div.gug-select-items > div:nth-child(%ddIdx%)
Use the "Run JavaScript function on web page" function to get the number of options available to the drop-down. (child elements)
The returned result is text, so convert it to a number that can be used in the loop.
function ExecuteScript() { /*your code here, return something (optionally); */
var firstDDlist = document.querySelector("#gug-overall-ranking-select > div.gug-select-items.gug-select-hide");
return firstDDlist.children.length;
}
In the loop each element will be pressed and cause the table to reload.
The table data extraction can then also be done in the loop, but that this code only shows the looping through the options.
The full flow 'code' (copy this and paste it in power automate).
WebAutomation.LaunchEdge.LaunchEdge Url: $'''https://dlv.tnl-uk-uni-guide.gcpp.io/?taxonomyId=36&/#gug-university-table''' WindowState: WebAutomation.BrowserWindowState.Normal ClearCache: False ClearCookies: False WaitForPageToLoadTimeout: 60 Timeout: 60 BrowserInstance=> Browser
WebAutomation.ExecuteJavascript BrowserInstance: Browser Javascript: $'''function ExecuteScript() { /*your code here, return something (optionally); */
var firstDDlist = document.querySelector(\"#gug-overall-ranking-select > div.gug-select-items.gug-select-hide\");
return firstDDlist.children.length;
}''' Result=> numberOfItems
Text.ToNumber Text: numberOfItems Number=> itemCount
LOOP ddIdx FROM 1 TO itemCount STEP 1
WebAutomation.PressButton.PressButton BrowserInstance: Browser Control: appmask['Web Page \'h ... sity-table\'']['Div \'gug-select-selected\''] WaitForPageToLoadTimeout: 60
END
It should end up looking like this:

Flow running:
