There’s no technical reason why you need to be using the same-named fork on desktop and Android; they will all communicate via Firefox Sync. e.g. I’m running LibreWolf (desktop) and IronFox (Android) with my data synced, but you could just as easily sync Zen Browser (desktop) and Fennec F-Droid (Android), etc.

That said, if you want to get both browsers from the same team/with the same branding, I think Waterfox is probably your best bet. It doesn’t have quite as strong a privacy focus as LibreWolf/IronFox, which both ship with very strict privacy-focussed defaults, which many users will likely roll back. For example, the default setting in LibreWolf is to delete all history and cookies on exit. Even so, Waterfox is more privacy-focussed than upstream Firefox and has released a statement on the Mozilla license changes if you want to get a feel for their perspective.