Hi @martial_L,
Thanks for your reliable, and it's better to use English in this forum, or you can find our French forum on the right top of the page.
Anyway, I'm not sure what you mean establish a connectivity relationship between Huawei's FIT AP or FAT AP and these Unifi Ubiquiti access points mentioned.
If you are trying to use the Huawei FAT AP as the gateway device, and connect the Ubiquiti AP to Huawei FAT AP to provide the wireless access for the users, it denpends on the Ubiquiti AP. If Ubiquiti could work as the FAT AP, yes, I think it could work to do that.