(I converted to an LLC in 2018), but I didn't actually lead or arrange any trips (it's a travel company) in 2019, so I made $0. I submitted the paperwork to close the LLC in 2019, since I wasn't making any money. I now need to mark final Schedule C, I believe. Should I just do that and not report any losses or can I still report my losses (even though I didn't make any money). Will it flag it as a hobby or something?
If you had ordinary and necessary business expenses in 2019 for an ongoing business, you should claim them.
As long as you were in business to make a profit, your expenses are deductible.
Showing a loss doesn't make the business a hobby, and not reporting losses doesn't make it a business engaged in for profit.
IRC § 183(d) provides a presumption that an activity is engaged in for profit if the activity is profitable for 3 years of a consecutive 5 year period or 2 years of a consecutive 7 year period for activities that consist of breeding, showing, training, or racing horses.
The Internal Revenue Service allows you to take a tax deduction for legitimate losses incurred in the operation of your business.