Cross join the two tables and take the MIN() of the result of making all the substitutions:

SELECT
  i.[id], MIN(TRIM(REPLACE(i.[Name], l.[Name], ''))) AS Name
FROM ImportedTable i
CROSS JOIN LookupTable l
GROUP BY i.[id]

See live demo .

Note that the convenient use of MIN() here only works when removing text from the end of text. It works because MIN() considers text to be "less" if characters are removed from the end, eg 'TestText' is "less than" 'TestTextKGal' .

Note also the use of TRIM(...) instead of LTRIM(RTRIM(...)) .

This solution will remove all text from the second tabe, which has text FROM the first independent of the position

I Expect that all pattern will only once occur, for multiple you must You need to repeat the first CTE until no more matches are found

the perfomance can be improve when you replace the LIKE CONCAT('%' , t1.[Name] , '%') with a full text search.

WITH CTE aS (SELECT
t2.[id],  REPLACE(t2.[Text],t1.[Name],'') resttest
FROM Table1 t1 CROSS JOIN Table2 t2
WHERE t2.[Text] LIKE CONCAT('%' , t1.[Name] , '%'))
SELECT * FROM CTE
  UNION ALL
SELECT  [Id],[Text] FROM Table2 
  WHERE [Id] NOT IN (SELECT [Id] FROM CTE )
ORDER BY Id

fiddle

Just another option which will support MULTIPLE occurrences of lookup values within the imported text .

Here, we convert your table into a JSON string and then do a Global Search & Replace via the Lookup table. Note the descending order of len([Name]) ... this will avoid any collisions (values within values).

Example

Declare @S nvarchar(max) = (  Select * from ImportedTable for JSON Path )
 
Select @S=replace(@S,[Name],'')
 From  (Select top 10000 * 
         From  LookupTable 
         Order By len([Name]) desc
        ) A

Select *
 From  OpenJSON(@S)
 with ( Id int
       ,Text varchar(500)
      )

Results

Id  Text
1   SomeText here 
2   500 
3   1.05 
4   105,000
5   TestText