If this is for internal use, I’d start by being very clear on whether “free” means no licence cost or just low effort, because the admin overhead can be the expensive bit. For simple scheduled seats, we’ve had the least pain with basic calendar/resource-booking setups tied to existing accounts, since people actually use them and you get permissions/auditing without building a mini app. If you need proper time slots, capacity limits, and reporting, the free options get thin pretty quickly, so I’d also think about how many users and how much conflict handling you need before picking something.