You know that you can increase Pd's debugging level and/or
start it with the -verbose flag to get more detailed error messages.
Does Pd post anything there when you start DSP?
Yes, I know, but there's no info about the problem, that's the main reason I came to ask here (for the first time in 10 years using Pd, btw).
On the jackd side: Are you getting any messages from jackd, for example
by looking at qjackctl's "Messages"?
I see nothing special from jackd side, looks like everything is working properly, and Pd shows up in patchbays like qjackctl and catia. Starting jackd via terminal with -v(erbose) and comparing 0.51.4 (audio ok) and 0.52.1 (no audio) the output looks the same.
And do you have a second alternative sound card you could try?
Not now, but it doesn't seem it will make a difference in this case. When I have my other sound card in the next few days I'll try again.
Do you think it's worth opening an issue on pd's github?
Thank you for the support,
Cheers