I think it's very unlikely that older Android tablets are supported by their manufacturers.
Of the 9 tablets and 8 phones in my sock drawer purchased since 2012, only the iPad Pro 10.5", Kindle Fire HDs, and Galaxy S8 are subject to continued upgrades. The rest are likely vulnerability Petri dishes that should never be allowed on the internet unless unlocked and moved to community builds (for the Android devices).
Of the 9 tablets and 8 phones in my sock drawer purchased since 2012, only the iPad Pro 10.5", Kindle Fire HDs, and Galaxy S8 are subject to continued upgrades. The rest are likely vulnerability Petri dishes that should never be allowed on the internet unless unlocked and moved to community builds (for the Android devices).