[linux/ubuntu] update README files
Revert "upnp: fire an update source message when a UPnP server becomes available/unavailable"

This reverts commit ff7416411df2d7f83906417232eee9466419be7b.
Revert "media library: add UPnP servers to sources://<mediatype>"

This reverts commit 762602329985513e071da34502a5b4af2ec83f65.
Merge pull request #5605 from yanniks/readmelnx

Update READMEs for Linux / Ubuntu
Merge pull request #5639 from Montellese/revert_upnp_sources
change spinners control for lists control after #5550

Changed mostly to list but I'm sure some should remain spinners.

This is here to fine tune with feedback from others
which should remain which should change.