You more or less got it. Currently you don't need to flash baqck to 2.0.1 there is a away to flash recovery directly to 2.1 and from there you install a custom (rooted) rom. However you still need to use RSDlite to do the flashing in both cases which (as far as I know) is a windows only program. Once you get recovery on the phone tho you can use linux for everything else, hell android itself is just a modified Linux.
You could just run a virtual machine of windows if you have no access to a win box
I Stand Corrected:
You can flash sbf files in Linux