Yesterday, after booting Windows on my old dual-booted laptop, I realized I had an old Firefox installation since 2016. One month ago, I installed Firefox without even noticing I already have it installed lol. And after looking at some files, there were files that had Firefox set as its default program to open, and... There it is... My old Firefox installation. The actual version there was 64.0 (2018), and my modern ass updated it to the latest version available. Lastly, I removed the new Firefox installation to maintain the old (and updated) one. Oh, and I installed Librewolf in there, on both Operating Systems (Linux Mint and Windows 10).