Yes, the whole rumor about Gerasimov’s death began with an image found on Discord of a purported message on a Telegram channel. The guy who runs the Telegram claimed it was a fake image.
https://www.newsweek.com/valery-gerasimov-dead-killed-crimea-attack-rumors-1858042
I never believe anything from any side until there is sufficient confirmation (and often there isn’t). Either Gerasimov is dead or he isn’t.
As for the “significant Russian figure”, who knows? The Express (British tabloid rag) is hardly known for accurate reporting on any subject. Lots of hysterical claims about lots of things.
The Express is run by MI-5 and MI-6 like most Brit media.