I’ve owned a raspberry pi 3b+ for more than two years and I’ve used osmc since. However, I’ve noticed that running osmc now almost always shows the lightning bolt symbol and the pi has become a lot slower overall. I have not made any changes to the power cable or the delivery system in any manner.
Can someone please suggest what could be the issue?
Power Supplies deteriorate overtime. I suggest to get a new one.
Your power supply probably isn’t up to scratch. You can learn more on our Wiki here: Frequently Asked Questions - Raspberry Pi - OSMC
I would also suggest to check your config text to make sure there is nothing set for voltage or CPU and memory speed. With kernel updates it sometimes changes how you can push it past stock. There was also a bug at one point where some of these settings could get set unintentionally so it is worth checking even if you don’t remember changing any of these.