How frequently do you recommend flushing a peritoneal dialysis catheter for patients with ESKD who are hospitalized and are not currently undergoing peritoneal dialysis?  

I'm not aware of any data to guide my response, just experience and "gut". It is our practice to flush unused peritoneal catheters on a weekly basis. 

We generally do them weekly but I have had situations where we go longer intervals, up to monthly, it makes sense that they should not need to be flushed often as some centers place buried catheters and they obviously can not be flushed until externalized.

Weekly max. I don't like people not familiar with the catheter using it for anything. Honestly, I might not even flush it.

I agree that our practice is to flush PD catheters once weekly. Crabtree et al., PMID 31028108 acknowledges that there is a wide range of catheter flushing policies across the country. The most common practice they describe is to use dialysate or saline (500ml to 1L) weekly until peritoneal dialysis...

We also generally do every week.

Generally, once a week to be done by an experienced PD nurse.