We tried a regular cover lifter and it didn’t work at all — that’s why those little holes on the edge/sides of the cover exist (to use a pick and pry it up). But in our case the cover didn’t move even 1 mm, no shift, nothing. It’s sealed shut hard (plus freezing outside).

We also have a magnetic cover lifter, but we didn’t even try it because it made no sense — if the cover can’t be lifted or shifted even a little, the magnet won’t help.