Do you want it to look like it was never damaged? If you aren't too concerned about the cosmetic result of the repair, epoxy will work just fine. If you want it to look like new, you can epoxy the plywood to fill in the dent, then try to heat the linoleum to soften it, and hot glue it back in place. If that doesn't look acceptable, you can try to obtain some replacement linoleum for a patch. Some times, you can find a small piece of linoleum you can cut for a patch under an appliance in an area that you won't see. You can also replace all the linoleum to make it seamless.
