Availability list / overview

Hello,

i'm looking for a practical and simple way to plan the presence of team members per day (day-based would be enough, hour-based is also great). I am looking for a self service possibility, so that every user can register if she / he has time on this day / how much time she / he has. I know the Shifts app, but I think it is too much for my purpose.

Does anyone know of a suitable app or native team functionality that makes this possible? At the moment I'm using Excel again and have built a template (looks like a calendar and every user has his/her own row per day and can therefore specify how much time he/she has per day) and included it as a tab in the channel.

Thanks!