How to trade not marketable steam cards?

Turn them into gems or trade them for TF2 metal - a lot of people are buying random cards

my friend got 75 unmarketable cards too, nobody want it :D so its pretty hard i think, ill be happy to provide him some info too what he can do

https://steamcommunity.com/id/VanillaBot
https://oy-vey-keys.com/
https://steamlvlup.com/

Read each bot/site info/faq what to do.

https://steamcommunity.com/groups/deaditems/discussions/0/
Myself i'm interested in non marketable to complete my sets.

Exchange it for 20 gems per card in the official Steam Trading Cards group.

https://steamcommunity.com/groups/tradingcards/discussions

This bot https://steamcommunity.com/id/VanillaBot is automatically set to accept 1:1 cross set trades for non marketable cards so that people can complete their sets. You can send trades using it's trade offer link https://steamcommunity.com/tradeoffer/new/?partner=350991682&token=l2wZSxL5