Seems like Voyager is a hit...

... but, I do offer another series of suggestions:

• Hubertos, the patron saint of hunters. In addition to linkages to a cure for rabies, he is the patron of hunters, which has fit with the lemmings and critters that we share online.
• Muroidea is the name for the superfamily of rodents, which you can read more about here.
• ~~Artemis is another series of manned space flights from NASA~~.
• Ulysses is another example. Add in it being a name of a mythological explorer, and it adds another layer.
• Mushak: Ganesh, from the Hindu pantheon, rides a mouse. This mouse's name is Mushak according to some sects. As a divine mount, there's some fun pieces of lore and how this app is how Lemmy users can ride into knowledge of the world around them.
• Ratatoskr is a Norse rodent, who carries messages on the world tree in that mythology. As this app shares messages and connects people, it's a fun way to share the core mission of Lemmy.

Those are some ideas! Hopefully some of this is helpful!