Can confirm this issue reproduces exactly as described on Linux (Mesa Intel HD Graphics 405 / Vulkan backend) using Prism Launcher on 26.4 Snapshot 2.
The superflat world generated fine at first. However, the exact moment I mined down two blocks and looked around to update the chunks, the integrated singleplayer server completely froze, going fully unresponsive.
Tested this scenario in 26.3 and fireworks are working exactly as expected. Right-clicking a rocket while standing on the ground doesn't trigger an action, which is normal vanilla behavior. The mechanics are working perfectly fine on my end.
Tested this out in 26.4 Snapshot 2 on Linux Mint 22.3 using Prism Launcher.
Set graphics to Fast to make leaf blocks completely opaque. When entering survival and teleporting my player's head inside the Oak Leaves block, no suffocation damage is taken (which is normal), but the screen remains completely transparent. The solid block overlay completely fails to load. Can confirm the bug reproduces exactly as described.