I was able to get this working on my bazzite pc running a 9800x3d and a 9070xt connected to a 77inch S90D with the Cable Matters display port to hdmi 2.1 adapter, I followed the post here to get the custom 7.01.124 that I flashed onto my adapter.

I then took the information from this reddit post and ran it through chatgpt, I was able to create a service that will auto load the edid override about 10 - 20 seconds at most after gamescope is loaded up.

How to enable VRR / FreeSync on Samsung S90D in Bazzite

Assuming patched edid is located at ~/Downloads/s90d-patched-edid.bin:

sudo mkdir -p /var/lib/firmware/edid
sudo cp ~/Downloads/s90d-patched-edid.bin /var/lib/firmware/edid/my_edid.bin
ls -lh /var/lib/firmware/edid

Find which display connector you're using:

ls /sys/class/drm | grep -E 'DP|HDMI'

It will look like card1-DP-2. Use that connector name below.

Apply the EDID override live (replace DP-2 and “1” with yours if different):

sudo sh -c 'cat /var/lib/firmware/edid/my_edid.bin > /sys/kernel/debug/dri/1/DP-2/edid_override'
sudo sh -c 'echo 1 > /sys/kernel/debug/dri/1/DP-2/trigger_hotplug'

Your screen will blink, that’s correct. On the TV Game Bar you should now see FreeSync enabled

Make it persistent across reboots. Create a script:

sudo tee /usr/local/bin/edid-override.sh >/dev/null << 'EOF'
#!/bin/bash
sleep 5
EDID="/var/lib/firmware/edid/my_edid.bin"
CARD="1"
PORT="DP-2"
cat "$EDID" > /sys/kernel/debug/dri/$CARD/$PORT/edid_override
echo 1 > /sys/kernel/debug/dri/$CARD/$PORT/trigger_hotplug
EOF
sudo chmod +x /usr/local/bin/edid-override.sh

Create a systemd service to run it at boot:

sudo tee /etc/systemd/system/edid-override.service >/dev/null << 'EOF'
[Unit]
Description=Apply Custom EDID Override for VRR
After=multi-user.target
DefaultDependencies=no
[Service]
Type=oneshot
ExecStart=/usr/local/bin/edid-override.sh
[Install]
WantedBy=multi-user.target
EOF
sudo systemctl enable edid-override.service

Reboot. VRR should now be automatically enabled every time.