How can I search for a specific word or phrase in SharePoint List items using filter queries?

Question

I want to get all SharePoint Online list items which contains a word or a phrase in one of their columns. I tried using contains operator in a filter query parameter, but it did not work. See below screenshot.

Reference: https://learn.microsoft.com/en-us/graph/filter-query-parameter?source=recommendations&tabs=http#operators-and-functions-supported-in-filter-expressions

I also tried using search query parameter for this, but it did not work as expected. It fetched all of the list items instead. See below screenshot.

Reference: https://learn.microsoft.com/en-us/graph/search-query-parameter?tabs=http

Please note that I cannot use the Search API for list items, because it does not support site-level search schema. In my case, I have this list already in production, with no site columns, but all list columns. Hence I do not have the default or tenant-level search schema that I can use here.

Please let me know if I am missing anything here. Thanks in advance!