Also I think you have a bit of a warped view on what an os update entails for Android devices, maybe because your only comparison is the iPad.

iPads need updates because it's the only way they can receive bug fixes and new features. On android even system apps can be updated via the play store, and new features can be added to your device via play services without even restarting, you'll just get a random info one day that says "your device can now do this or that". (Unless you go without play service ofc).

OS updates for the last few years have just been pretty forgettable stuff (like I can't even remember one single feature they added with Android 14, I think it was just new clock fonts?)

As for hardware quality, I've had my Tab S5E for years, and it is super solid. It looks, feels, and sounds great. It's one of the few samsung devices that can be unlocked and Lineage installed on. So, if you're willing to put in the time to install Lineage on it, it's android 13 and the newest version of Lineage on it.

I don't think any manufacturer offers more than 5 years os updates. Normally you will still get security updates afterwards but I don't know if there is any way to see how long exactly beforehand.
If you install lineage or some other rom it would not matter anyways what the official support is. But someone needs to take the time to port it to your device, so the more popular of a device you choose the more likely it is to get ports longer.

Generally I'd recommend looking at what hardware of a popular device fits your needs (size, budget, pen etc) and then just looking at xda to see what roms are available and how easy the flashing process is.

I don't understand what you mean by saying you don't want the software bricked in 5 years. You mean bricking while flashing a rom? Usually that's easy to recover. I don't think I've heard of many people bricking a device unrecoverably lately.

I highly recommend the Pixel Tablet with GrapheneOS. It gets 5 years of updates, and it's very secure. Especially with GrapheneOS. Just like Pixel phones.

With the currently available Android tablets the software really limits its uses. Many of the higher quality product focus too much on productivity without success. But this creeps up the prices so much that makes them hard to justify for entertainment.

I think there are only a few use cases where tablets shine:

• A small (and cheap) reader that's a comfortable in one hand with a decent screen resolution. It works great as a big phone to enjoy reading comics, books, websites or browsing social media. The Tab S6 Lite 2022 is a solid 10" option and chinese brands offer 8" tabs like the Doogee T20 Mini. You won't get long software support but the price makes it somewhat acceptable.
• An Oled multimedia screen. These are great for all kinds of videos, movies and series. There are just a few options like the P11 Pro Gen2 that are affordable.

Longer software support is only available from just Samsung or Google and I can't justify the prices of those if a laptop can replace it. Here a Pixel Tablet or a Tab S9 costs the same as 13" laptop with oled screen (Zenbook S 13) with "unlimited" software support.

I do own a T20 Mini and an old ThinkPad and I really like reading on the Android tablet even with the slow SoC and medicore screen, but bring a real laptop along for longer trips.

Looks like the Pixel Tablet has 3 years of OS updates and 5 of security.

https://support.google.com/googlepixeltablet/answer/13555449?hl=en&ref_topic=13075701&sjid=2970932514574952490-NC#zippy=%2Cwhats-the-os-update-policy-for-the-pixel-tablet

Side Of Burritos made an unboxing video + GrapheneOS test of the Pixel Tablet: https://youtube.com/watch?v=jfbz1RzSJh4

This was 7 months ago so you should assume that GrapheneOS got even better now.