Embedding a Lightning node into everything that accepts payments would certainly be the most reliable solution. However, every time I come up with a similar idea, I always get stuck on the question of where to source the Bitcoin node to use as the backend for LN.

Unlike other so-called "decentralized" coins, Bitcoin doesn't have a "foundation" running public nodes. As long as I control my private keys, using a Bitcoin node operated by someone else for a small fee wouldn't be a huge issue. But would it make sense to think of it that way?