Is Signal app a fail except for phone only use?

After latest update (6.25) there is no linking possibility with any non phone device.
Tablet, notebook, desktop DO NOT sync for me in any way.

Is this just me who has issues with this Signal claim?

Signal can only be used on one mobile device and up to five linked Signal Desktops.​

It works fine on my end, so no, no “issues with this Signal claim”.

Instead of starting off with calling Signal into question, you could ask “has anyone else gotten the same issue?” or “does anyone knows what might be causing this and has a solution?”

What OS do you use? Have you tried uninstalling Signal from the device (laptop, tablet, etc) you want to link and reinstalling it?