If someone else faces that problem with Silverblue or another immutable variant, here are the steps I took to revert to mutter-48.2-2 (the version before the bug):
First, I downloaded the commit history of the last 10 days
sudo ostree pull fedora:fedora/42/x86_64/silverblue --commit-metadata-only --depth=10
ostree log fedora:fedora/42/x86_64/silverblue
Then I checked the differences day by day and found the commit from May 26 to contain the older mutter version.
rpm-ostree db diff 71a337e442a2dc36df79e123bb5011a1ffc5e2bd0ce8aac61157fd6ecd477491
After that, I downgraded my system with rpm-ostree deploy 71a337e442a2dc36df79e123bb5011a1ffc5e2bd0ce8aac61157fd6ecd477491 and pinned the deployment with sudo ostree admin pin 0 so I would have a working system until the fix is published.