Attempts to do this trustlessly without relying on a liquidity provider do exist, but they're not mature enough to mention yet. They usually rely on zk proofs to validate that an asset was bridged from one chain to another.
L2s are presently already supporting more activity than L1, with 4 L2s regularly doing more TPS than L1. Agreed that fragmentation is a concern, but I think we'll get there soon where the UX is abstracted away for users and the assets flow cheaply.
There are bridge providers like Connext (https://www.connext.network/), Hop (https://portal.arbitrum.io/projects/bridges-and-on-ramps?pro...), LayerZero (https://layerzero.network/) etc that provide liquidity across L2s to make it simple and cheap for common assets like USDC, ETH, etc.
Attempts to do this trustlessly without relying on a liquidity provider do exist, but they're not mature enough to mention yet. They usually rely on zk proofs to validate that an asset was bridged from one chain to another.
L2s are presently already supporting more activity than L1, with 4 L2s regularly doing more TPS than L1. Agreed that fragmentation is a concern, but I think we'll get there soon where the UX is abstracted away for users and the assets flow cheaply.