I have a 9th gen (2019) so it's probably different. I searched and found this in an early post for FTB V7.1 by Datastream33:Yes, I have tried different launchers
It might just be a limitation of 7th gen and below tablets.Custom Launchers. In this update we also have a subtool that belongs to the 7th gen and below families. The subtool "Downgrade Fire Launcher" presents the ability to downgrade Fire Launcher to a previous version and allows the user to launch a third-party launcher in Fire Launcher's place. While this method isn't perfect and can sometimes take a few seconds it still is a much more reliable method as it will not take longer then 5 seconds (like the Launcher Hijack method does). Then only downside is it must be applied after every shutdown or reboot.