I looked through the aurwiki for arch and there is nothing either. Even though lemmy has been around for a little while, it really wasn’t as mainstream as it is after the Reddit migration. ~~Give it a little time and someone might make one, but I think pretty much everyone is using web browser or an app on their phone for access atm~~ I stand corrected, there is a desktop app for Lemmy app for linux on flathub called lemoa
flatpak install flathub io.github.lemmygtk.lemoa