You could choose
Sort by (type}, which would separate out all the different file types, which would make selecting each file type easier.
Or...
Use
Find... (Cmd F) and search for the word "
.jpg" - which has the advantage of automatically selecting all the unwanted jpegs, which you can then quickly and easily delete (Cmd Backspace).
You may want to ensure you're not viewing
Combining RAW+JPEG (Cmd J), but I haven't got a folder of raws & jpegs to test whether it's a necessity - probably is tho'.
Here's a screenshot of the settings I used when I quickly tested my theory (the jpegs can be seen to be selected and the tiffs unselected, from when I first ran the
Find... command)
There's bound to be other ways of achieving this, this is just the method that occurs instantly to my tiny brain.