Looks like @manuel.sailfish found a very recently reported issue: fix: update link device params with spqr by dudufalvo 路 Pull Request #415 路 whisperfish/libsignal-service-rs 路 GitHub, which means that linking is broken altogether, but this will be fixed in the next version of Whisperfish! 
I鈥檓 quite busy until the 17th, but I will with high probability join Next meeting for French-speaking Sailfish OS users : 21 March 2026 in Lyon for a bit of a hackathon, I鈥檝e heard!