Pfft, Hellblade 2's development taking so long has not been because of UE5. They were still location scouting in Iceland in 2020, they were still crafting the vertical slice last June. Hellblade 2 is taking so long because they were nowhere near as far along in 2019 as we had hoped, and they're still not done because they are still not done, not because UE5 is not done and they can do nothing but twiddle their thumbs and wait. They're still making the game.
People are building their games in UE 4.2X, which is stable and has some UE5 or otherwise newly-introduced UE modules, and they're testing with UE5 EA and the new Preview build (which GSC, Ninja Theory, and The Coalition may already have a candidate of, being pilot partners for Epic.) They can work with everything they need to for a stable project now, and they can start integrating future aspects of the engine as it comes online and passes compatibility in testing with their current techstack. That is in all likelihood where GSC is, with tools and assets and a workflow that was all in place long, long before they ever had any access to UE5 (maybe even a tip that UE5 was coming.) The timeline doesn't add up otherwise. If there was any fear UE5 wouldn't be ready, there would have been no reason to jump to UE5 when they had a working slice of the game already last January. It would have been suicide in 2020 to look at all of that transformative tech Epic was to be introducing with UE5 (and that Epic has been clear from the very beginning was & still is WIP, despite the stability) and say to themselves, "Epic hopes on launching at like Christmas or something, so should we pencil our game launch in for April?" GSC didn't make its date for the same unfortunate reasons as nearly every other game studio using whatever engine has not landed their initial launch plans these past two years. It's hard making games, and dates sometimes can't stick. And reading through this thread, very few people are surprised or angry about STALKER's situation; April 2022 seemed optimistic to many, and people had hope but were holding their breath for it...
And BTW, already two consumer game products using Unreal 5 are out on the market: Fortnite and the micro-game (if you will) Matrix Awakens. Both are still by Epic (and Epic partners, including The Coalition,) but they're stable on home consoles and playable for consumer use (and even though Fortnite came out later than expected, Matrix nailed its release deadline, proving a necessary level of reliability of the engine.) And developers have been doing a lot (some even making release products) using Early Access since May. UE5 has held studios to the lightest mercy in the history of Unreal Engine (and maybe any game dev engine) rollouts.