Having the stock available on multiple exchanges does bring...

Having the stock available on multiple exchanges does bring about arbitrage opportunity, however obviously other markets do not have anywhere near the liquidity that the ASX holds for Magnis.

The difference in share price can be used for multiple purposes. The purchase of shares in URNXF could determine an increase in SP on other markets. This could also be seen as an overvalued SP and shorters could use this to their advantage if able.

If you believe the company is already undervalue or expect the SP to increase, an investor is able to essentially purchase the shares at a discount to their home trading price. In this instance that would be U1P on Frankfurt Stock Exchange which is currently trading at a discount to MNS.
In saying this, U1P has only 1 bid at €0.263 and 1 offer at €0.302 so liquidity does not necessarily provide that opportunity easily.

Anyway, nothing significant or important there, just something to consider