Is the salary earned from working as an agricultural engineer in a tourist hotel that sells alcohol and encourages immorality considered unlawful (haram), even though the nature of the work is far removed from these matters?

If your work does not involve assisting in a forbidden matter, then there is no harm in your work or in the salary, and it does not concern you that the salary comes from the hotel's mixed income. However, if your work involves assisting in a forbidden matter in any way, then it is forbidden because it falls under cooperating in sin and aggression. You must leave it unless you are compelled, in which case it is permissible to remain in it until you find a permissible alternative. You must then donate the portion of your salary that corresponds to your assistance in the forbidden act to public welfare and charitable causes.