How to remove burned grease from bottom of stainless steel skillet?

Try Bar keepers friend

https://www.apartmenttherapy.com/how-to-clean-burnt-pots-scorched-pans-140547

HAVE YOU TRIED BAKING SODA AND VINEGAR?

Hi Liz. I use Bar Keepers Friend. It makes my pots and pans look brand new.

Use 1 cup of baking powder and 2 cups of water and bring those to a boil in your pan. Allow it to boil for awhile, then pour out and the hunk should come off easily.

A paste of baking soda and water, apply and let it sit with the bottom up, check back in a few hours and see if it has lifted off with mild scrubbing. Can redo it not.

Put a layer of white vinegar in pan to cover bottom. Sprinkle baking soda over making sure to cover burn spots. Let fizz and set for long while, then scrub out. It usually does the job for me. If any little left over I use a brillo/sos pad to finish.

Put some hot water and a dryer sheet in it and let it soak.