Checking keywords from another table

Let's assume that column is named Data in both tables. Then in a custom column in Table2, you can put following formula

= try Table1[Data]{List.PositionOf(List.Transform(Table1[Data],(x)=>Text.Contains([Data],x)),true)} otherwise null

See the working here - Open a blank query - Home - Advanced Editor - Remove everything from there and paste the below code to test

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WcnRy1jVWitWJVkoEMl3ArEgPT28ww83d3R3M8PL29gIzXFwd452UYmMB", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Data = _t]),
    #"Added Custom" = Table.AddColumn(Source, "Result", each try Table1[Data]{List.PositionOf(List.Transform(Table1[Data],(x)=>Text.Contains([Data],x)),true)} otherwise null)
in
    #"Added Custom"

Here's another possibility.

(row) => List.First(List.Select(table2[Keyword], each Text.Contains(row[Text], _)))

This takes the list of keywords (table2[Keyword[), selects the keywords that are contained in the text from the current row of table1, and then takes the first element of that list (if it exists).

Full sample query (referencing table2 with a column [Keyword]):

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WcnRy1jVWitWJVkoEMl3ArEgPT28ww83d3R3M8PL29gIzXFwd453ALJBqVzeIdERklFJsLAA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Text = _t]),
    #"Added Custom" = Table.AddColumn(Source, "Custom", (row) => List.First(List.Select(table2[Keyword], each Text.Contains(row[Text], _))), type text)
in
    #"Added Custom"