Struggling with Christmas Cactus — would appreciate advice

I want to be honest: I'm not getting great results with Christmas Cactus and I'm not entirely sure why. root rot from any waterlogging in winter has been a recurring problem despite my attempts to address it. I've been focusing on protecting from frost below -5°C even for hardy varieties based on everything I've read.

remarkable drought tolerance once established is there in glimpses, which tells me the plant has potential in my conditions. I have it in a greenhouse or conservatory staging which might not be ideal. flowering in late spring to early summer showed some improvement. Two stars for now — not the plant's fault, but not a success yet. I'll update if things improve.