How long have you owned these older-generation speakers? They must have worked for you at some time in the past. 
 

Yes, you can set Auto-play for the line-in, but the speaker needs to be on the network in order to configure it. 
 

Since you’ve “tryed �sic] all fixes” you might as well give them away, as you say. Or shoot them. 

Here are the Sonos System Requirements…

https://support.sonos.com/en-us/article/sonos-system-requirements

These are the mobile controller requirements…

https://support.sonos.com/en-us/article/sonos-app-requirements

Once the system is setup, then select the line-in settings on your device and enable autoplay. See these links:

• https://support.sonos.com/en-us/article/use-line-in-on-sonos
• https://support.sonos.com/en-us/article/adjust-line-in-settings