Ok I was finally able to connect, back up, bootloader unlock and root my stylo 6.
I could never get the phone to connect with SPFT and mtkclient.
What I eventually did was open the phone and short the test points. (Mobo had to be removed, test points are on screen side of board)
After doing that the phone will connect instantly to mtkclient, and in my case I had no need to use SPFT at all.
Also I updated to latest firmware with Feb 2022 security patch and could still connect no problem and flash boot images.
Hopefully this helps anyone like me who can't get a connection to their phone otherwise.
Thanks to @Warlockguitarman
for the tutorial, nice job!