I heavily use Firefox for Android on multiple devices since many years. It HAS annoying bugs. The most annoying for me is the tab view keeps forgetting the last tab you were on, when for example closing a tab from tab view or moving between tabs by swiping the address bar.
I think every person's bugs depends on how they use the software.
edit: quick word order fix.
If you have dual GPUs or an iGPU plus a GPU, you can use passthrough and play your games with near native performance in an isolated Windows virtual machine under Linux.