So it is not just cyber warfare, hybrid warfare, grey-zone warfare, but now 'planned false flag accusation' warfare.
Less than a month ago the similar allegations were made by Russia against the USA:
"American mercenaries preparing ‘chemical weapon’ incident in east Ukraine, Russia claims"
https://www.newsweek.com/ukraine-rebels-russia-claim-imminent-chemical-disaster-us-urges-calm-1662031
As for alleged 'cyber-attacks', the Wikileaks released 'Vault 7' in spring 2017, made it perfectly clear that the CIA had long had the ability to forge IP addresses, where they originated, and leave 'fingerprints'( Chinese,Russian, N. Korean, et worldwide languages script cetera ) fingering anyone but themselves.
https://eu.usatoday.com/story/news/2017/03/07/wikileaks-cia-hacking-group-umbrage-stockpiled-techniques-other-hackers/98867462/
Vault 7: CIA Hacking Tools Revealed
https://wikileaks.org/ciav7p1/
Might as well trust the veracity of Boris Johnston, or, as youngmafbog astutely said, "The reality is, who really knows the truth?"