Well...
TBH, I've not seen a battery bulge (in a tablet... seen plenty others...), but I do have a tablet which doesn't seem to hold it's charge as well as it used to.
So, have I done in-depth long-term testing... no.
Personally, I just got some of these USB switches and was more interested in whether I could control it easily (I could)
Re: LineageOS - yeah, I agree, if you can find the right tablet AND it's supported, then definitely flash it.
You might still need to download the latest webview component though.