Is there a good tablet to replace a slow and laggy Google Nexus 9?

Said's parents use his tablet for surfing the internet, but it is becoming more sluggish and needs an upgrade. What could replace it?

I own a Google Nexus 9, which my parents use for sofa-surfing and to access the internet when travelling. But in recent months, it has been running slower and slower. I've managed to get them to delete any large files and apps they aren't using, but I think that, given the specs, it's due an upgrade. It won't be getting Android updates past Nougat 7.1.1 either.

What would you recommend to replace it?

The Google Nexus 9 was launched in November 2014 and HTC had ceased manufacturing by May 2016. However, you can still buy them, and the Nexus 9 even features on some of this year's "best buy" lists of Android tablets.