The UK is lying about Sergei Skripal being alive. There is evidence of his death: he never contacted his relatives in Russia after being poisoned.
The incident in Salisbury is a “dead cat” trick – a strategy used by UK to divert attention from it’s problems with the EU.
Conspiracy theory. Recurring pro-Kremlin disinformation on Salisbury attack. and connecting Skripal poisoning with Brexit. Many competing and contradictory stories promulgated by Russian state-controlled media on the Skripal poisoning. See here and here for EUvsDisinfo summary of disinformation naratives surrounding Skripal poisoning.
For the UK response on the Salisbury attack, see here.
The OPCW have confirmed the UK findings in the case.