There is Fennec available on F Droid that is basically Firefox with some blobs removed. Not as hardened as Mull but still a worthy option. There is one more browser based on Firefox called Iceraven for Android but it is not available on F Droid even. Though it supports a much wider variety of extensions than mobile Firefox does as of now. The downside is that it gets security updates usually later than Firefox, being an independent project.
There is Fennec available on F Droid that is basically Firefox with some blobs removed. Not as hardened as Mull but still a worthy option. There is one more browser based on Firefox called Iceraven for Android but it is not available on F Droid even. Though it supports a much wider variety of extensions than mobile Firefox does as of now. The downside is that it gets security updates usually later than Firefox, being an independent project.