Since the name comes from
Carolus Linnaeus's surname. The pronunciation's a bit more obvious too, though personally I think
Linnaea looks messier than Linnéa.
But Linnéa, with the accent, is pretty straightforward imo. After all, most people in English-speaking countries know that
é equals the AY sound, due to common names like Désirée and Renée.
I really wouldn't spell the name in any way else other than
Linnea or
Linnaea, personally. Anything else just looks kre8iv and--truthfully--a bit ignorant to me.
Miranda