No. L-plates are not limited to Arca-Swiss. Manfrotto has made L-brackets for its own quick-release systems, so Arca-Swiss is not the only option.

That said, Arca-Swiss-style dovetail plates are much more common in higher-end support gear, and many photographers prefer them because the system is widely supported, precise, and flexible across different heads, clamps, and accessories. Camera-specific anti-twist and L-plate options also tend to be easier to find in the Arca ecosystem.

So the short answer is: yes, Manfrotto-compatible L-plates exist, but Arca-Swiss has broader support and is often considered the better long-term system if you’re building out a support setup.