I freeze without mash, but I've frozen with mash before and it's been OK, especially with grated cheese on top for last 10-15 mins of cooking.
I make fish cakes and freeze on a tray and then put in a bag. I also make veg ones - essentially mash with some chopped cooked carrots, onion, peppers and frozen peas and sweetcorn mixed with grated cheese. I make a batch of each, shape, dip in egg and then breadrumbs.
I made individual cheese and vegetable pies the other day and froze two uncooked - they were successful. Rough puff pastry with a filling of cheese sauce and vegetables (like the supermarket ones).
When I make pizzas, I make an extra one and half cook it. Cool it and cut into quarters for freezing.
Lasagne. Veg version for us, so veg in ragu layered with cheese sauce and lasagne sheets.
I cook and freeze, so that my husband can prep dinner by putting something in air fryer and cooking some veg or making a salad to go with it. He hates cooking, but he finds it doable, and we all get a decent meal after work.