Not every “Reddit alternative” is on the Fediverse.

Check out PolyCube for a modern 3D Tetris.

https://store.steampowered.com/app/798790/PolyCube/

Does KDE Connect do what you want?

Maybe a better term is field-replaceable batteries. It’s great for the longevity of a device to be able to install a new battery in a few minutes with just a screwdriver, but I miss the earlier days of cell phones where you could keep a spare battery in your bag while out and about and swap it out with the dead battery in your phone in just a couple seconds.

You can, but users on their instance can’t