Is money earned from working on a computer purchased with mixed funds (mostly unlawful) considered unlawful money, knowing that everything related to the internet (internet card, subscription, and work expenses) was financed with lawful money?

If the earned money is a result of legitimate transactions, then purchasing a used device with money mixed with unlawful (haram) funds does not affect it. This is because the unlawfulness of the money pertains to the liability of the one who acquired it, not to the specific item it was used to purchase. The method for disposing of unlawful money is to return it to its owner or their heirs if its source is known. If this is not possible, it should be given as charity on behalf of its owner. However, if the unlawful money is a compensation for an unlawful benefit, or does not belong to a specific owner, such as usurious interest, then it should be given as charity to the poor and needy, or spent on general public interests of the Muslims.