When the AC remote can't be found in the database the setup should offer you the teaching mode, so you could record the commands from your remote.
If this hasn't happened, I'd advise to please contact our support with the specific details of your system. Please, add pictures of the front and the back of your remote for our team to be able to help you more efficiently.
Edit: Since the original answer was posted, our setup process has been changed. Teaching mode is only avaiable with Smart AC Control previous versions. If you have a V3+ version, please contact support whenever your remote is not recognized.
Any update about this bug? I cannot Get my Tado configured properly
If you would buy a V2 Smart AC Control, then it would be possible to train but Homekit is not supported.