hi Christian,
I had another issue with an ATU100, where the OLED made noise every 1080kHz up to 30MHz...
Search the regulator on the back, then do a try... ( mine is a 0.96inch OLED)
I know, where RF comes out, RF also goes in...? I think, it's worth to make a try.
(I don't know, how many capacity the IIC-bus can drive. On the board there are just 1nF installed on SCL and SDA)
73, Immo
Immo, DL5KB