Reimbursements of actual expenses are not taxable. You'll get a 1099-LTC with Box 3 indicating that the amounts were reimbursed expenses. You'll file Form 8853 showing nothing is taxable.
But if they are paid on a per diem basis, Box 3 will indicate per diem and any amounts in excess of the actual expenses OR an excluded minimum are taxable. The excluded amount changes each year and can go up or down ($390 for 2022, $420 for 2023, $410 for 2024). So if the actual expenses amounted to $300/day for 2023, they would only have to pay taxes on payments in excess of $420/day. If actual expenses amounted to $500/day, the excluded amount is irrelevant and they pay taxes on payments in excess of $500/day. (You look at the totals, not the actual per day expenses)
Accelerated death benefits from life insurance are reported in Box 2, but are not taxable if terminally ill (otherwise, they are treated as Box 1 amounts and are only taxable to the extent they exceed expenses or the excluded amount).