LÖVE

Where's the guide/how does one make an apk (doesn't need to be uploaded to playstore, just to be able to be installed on modern devices). Also is there a way to make an aab(?) file...

Wiki?

https://love2d.org/wiki/Game_Distribution#Android

Ooh, nice. I even missed the aab part.
But I'm a little bit confused on how to sign an apk (since t says it can't be installed unless signed) using APKtool.

Or could I really just use love action? I browsing on my phone right now so I can't tell exactly how it works. Is it am executable?

(Also, Slime and co. nice work, I was about to post a topic asking why the colours look off in some android devices I test on, but I see 11.5 fixed that )

Signing an application is more in the realm of Android guides in general, than anything LÖVE specific. It's just something you have to do, if you wish to upload to Google or Apple's storefronts. Distributing outside these stores, you can sort of sidestep the signing process, but users might need to do some extra steps (effectively permit their device to run an unsigned app) to get your application running.

You can make an APK & aab with android studio. You can find instructions here.