I seem to recall from a year or so ago briefly testing some Shimano L-422 Light Action downtube friction shifters with an 8-speed cassette and Shimano 600 Tricolor 8-speed RD. Worked fine if I'm recalling that setup correctly. I know I also used those shifters on another bike with 7-speed freewheel, but that's easy.
I have some Dura Ace 10-speed bar-end shifters, mostly used with aero bars on a TT/tri-bike, but haven't tried the right/rear shifter in friction mode. Seems like it would be very finicky. I have used my Ultegra 8-speed bar-end shifters with an 8-speed cassette setup and nominally 7-speed Deore LX RD, no problem. That rear derailleur doesn't pivot/swing quite far enough to shift reliably into the big cog in index mode with an 8-speed cassette, but will in friction mode.