See this variant - choke input filter (10H/100 Ohms/200mA) with "tuning" C1=1,5µF/600V (MKP, MKT...), then C2=220µF/450V electrolitic.
Bypass C2 with "bleeder" resistor, Rb=27kOhms/5W (it draws 8mA).
Then split for two channels - L2/C3 + R1/C4 for the L channel, and identical LC+RC filter for the R ch.
You`d get about 213V for the output stage, and 207V for the driver.
Of course, Rtr is a guess, and maybe you`d need to adjust the value of C1. Caps C3 and C4 can be "motor run", or MKP/MKT, 400Vdc ratings.
BTW - if you choose to build it, you can post on "Group Build" (Tube DIY) forum...