I see - probably the Nujno (urgent) checkbox on a SEPA form activates this SEPA instant payment. I know about Flik and I like the appeal of it, but I do not us

I see - probably the Nujno (urgent) checkbox on a SEPA form activates this SEPA instant payment. I know about Flik and I like the appeal of it, but I do not use it because it requires a proprietary client (NLB Pay in my case). Do you know of any public or reverse engineered specification or unofficial FOSS client?