We can confirm Makaton on Mixmups is working as expected, as it shows the Makaton signs at the start of the episode, but not throughout the episode as you would get with the BSL option.
Makaton is not a language, but a system of individual support signs taken from a limited repertoire of signs and should be delivered alongside spoken English. It is primarily used by hearing people with learning disability and unlike BSL, it does not have it's own unique grammar. It is more a labelling system and it is not possible to communicate in Makaton without also voicing over simultaneously, whereas BSL is a visual language and can be understood visually, so can sit alongside spoken dialogue.
We consulted extensively with the Makaton Charity in the UK, who felt that stopping and starting the episode to interject single Makaton signs with voiceover was not appropriate for the audience. They decided they would like key Makaton signs to be delivered with voice at the top of the episode to support concepts and in preparation for the upcoming episode.
Makaton options are available with episode key signs for each episode. There is also an option to view series signs in the Prep menu.