himbim Did you by chance enable the snap store on Linux mint 21.2? It's disabled by default. If so, did you download Chromium from there? It won't work because the snap release has broken WebUSB.
Open instructions in Chromium
Do you have multiple instances open of the web installer, ie., loaded in different tabs, or at the same time in different browsers (both in chrome and chromium?)
Chrome installed: 119.0.6045.105 linuxmint1+victoria
Have you tried restarting your computer, make sure you only have 1 instance open of the web installer (no other tabs or browsers). Are you using the included stock usb cable? Are you using any sort of usb hub or adapter? Have you tried a different port?
How can I flash the phone, can someone help, please?
This is most likely a problem with your usb connection. It is not being recognized by your laptop after it restarts.
I waited 15 minutes, nothing happened.
When that happens, you could try to unplug the cable and then plug it back in, perhaps it will continue from where the installation process left off.