I have a Lulzbot 6 which has been working well. I purchased a Flexystruder v2 and upgraded Cura from Cura 21.08 to cura-lulzbot 2.6.66 as suggested in the instructions. However, it fails to load any STL files. I am running Windows 10 on a HP notebook, but have also tried it on a HPZ240 i7 with 32GB memory.
When upgrading from Cura 21.08 to Cura LE 2.6.66 there are a couple of additional steps that need to be taken to ensure everything works as expected. I had a few issues when upgrading but it seems to be working okay for now.
Go ahead and retry the process (starting off by uninstalling both versions of Cura, clearing all cache files, redownloading the latest version of Cura 2.6.xx)
You can find the detailed instructions here: https://www.lulzbot.com/learn/tutorials/cura-lulzbot-edition-installation-windows
Be sure to clear the cache files before installing Cura 2.6.66.