I just repaired my Sonos Connect that stopped working after about 10 years in operation.
Symptoms: No correct boot, flickering front LED, no connection nor sound.
After opening in line with the Fixit guide, I found smoke marks around the largest capacitor on the power supply board. Other parts just had some smoke marks but after careful cleaning no other signs of destruction.
Thus I ordered a new 22 μF 400V TH 105°C Elko, cut the connections of the old one at a distant of about 6mm from the PCB (did not want to solder on the board directly), put some insulation around the Elko (as it touches some the PCB components) and soldered it to the 6mm connections.
After closing the casing, plugging in the power and the ethernet, it connects and plays the music as before.
All above is very simple without the need of removing any boards.
(The Elko was about 2 EUR but is surely cheaper if you have a good source).
As often, electronics problems originate from the simple components!
Hope this helps.