The monitor that my device is attached to (https://www.samsung.com/us/computing/monitors/uhd-and-wqhd/34-sj55w-ultra-wqhd-monitor-ls34j550wqnxza/) is capable of outputting at 3440x1440@75Hz. This monitor when used with Windows 11 and the same device will run at 3440x1440@60Hz maximum due to the availabel graphics processor. On Fedora 38, with Wayland or on X11, it will only output at a maximum of 3440x1440 at 49.99Hz.

Reproducible: Always

Steps to Reproduce:
1.Enter display settings
2.Select the external monitor
3.View refresh rate options
Actual Results:  
Monitor outputs in 49.99Hz at 3440x1440

Expected Results:  
Monitor output should be able to output in 3440x1440 at both 60Hz and 75Hz.

I have verified that the monitor supports the output of 75Hz using the monitor-edid tool which returned the following:

[chenderson@chenderson-personal card1-eDP-1]$ monitor-edid
Name: S34J55x
EISA ID: SAM0f71
EDID version: 1.3
EDID extension blocks: 1
Screen size: 79.7 cm x 33.3 cm (34.01 inches, aspect ratio 2.39)
Gamma: 2.2
Digital signal
Max video bandwidth: 410 MHz

	HorizSync 30-120
	VertRefresh 50-75

	# Monitor preferred modeline (60.0 Hz vsync, 88.8 kHz hsync, ratio 2.39, 109 dpi)
	ModeLine "3440x1440" 319.75 3440 3488 3520 3600 1440 1443 1453 1481 -hsync +vsync

	# Monitor supported CEA modeline (60.0 Hz vsync, 67.5 kHz hsync, ratio 16/9, 61x82 dpi) (bad ratio)
	ModeLine "1920x1080" 148.5 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync

	# Monitor supported CEA modeline (50.0 Hz vsync, 56.2 kHz hsync, ratio 16/9, 61x82 dpi) (bad ratio)
	ModeLine "1920x1080" 148.5 1920 2448 2492 2640 1080 1084 1089 1125 +hsync +vsync

	# Monitor supported CEA modeline (60.0 Hz vsync, 45.0 kHz hsync, ratio 16/9, 40x54 dpi) (bad ratio)
	ModeLine "1280x720" 74.25 1280 1390 1430 1650 720 725 730 750 +hsync +vsync

	# Monitor supported CEA modeline (50.0 Hz vsync, 37.5 kHz hsync, ratio 16/9, 40x54 dpi) (bad ratio)
	ModeLine "1280x720" 74.25 1280 1720 1760 1980 720 725 730 750 +hsync +vsync

	# Monitor supported CEA modeline (59.9 Hz vsync, 31.5 kHz hsync, ratio 3/2, 22x36 dpi) (bad ratio)
	ModeLine "720x480" 27 720 736 798 858 480 489 495 525 -hsync -vsync

	# Monitor supported CEA modeline (50.0 Hz vsync, 31.2 kHz hsync, ratio 5/4, 22x43 dpi) (bad ratio)
	ModeLine "720x576" 27 720 732 796 864 576 581 586 625 -hsync -vsync

	# Monitor supported modeline (50.0 Hz vsync, 73.7 kHz hsync, ratio 2.39, 109 dpi)
	ModeLine "3440x1440" 265.25 3440 3488 3520 3600 1440 1443 1453 1474 -hsync +vsync

	# Monitor supported modeline (60.0 Hz vsync, 66.0 kHz hsync, ratio 2.37, 81 dpi) (bad ratio)
	ModeLine "2560x1080" 198 2560 2808 2852 3000 1080 1084 1089 1100 +hsync +vsync

	# Monitor supported modeline (60.0 Hz vsync, 88.8 kHz hsync, ratio 16/9, 81x109 dpi) (bad ratio)
	ModeLine "2560x1440" 241.5 2560 2608 2640 2720 1440 1443 1448 1481 -hsync +vsync

	# Monitor supported modeline (60.0 Hz vsync, 67.5 kHz hsync, ratio 16/9, 61x82 dpi) (bad ratio)
	ModeLine "1920x1080" 148.5 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync

	# Monitor supported modeline (75.0 Hz vsync, 111.9 kHz hsync, ratio 2.39, 109 dpi)
	ModeLine "3440x1440" 402.75 3440 3488 3520 3600 1440 1443 1453 1492 -hsync +vsync


As you can see from the above the monitor edid does show the 3440x1440@75Hz and the 3440x1440@60Hz option so it is supported so I assumed that the issue was something to do with Wayland.
Note that the monitor is connected to the device via a USB-C hub using the DisplayPort over USB-C protocol however I have also tried connecting the device directly with the HDMI port from the device to the monitor and the problem persists.
Note that the device connected to the monitor supports only 60Hz at 3440 so the maximum 75Hz is not available in this instance regardless however the 60Hz should be available.

From the Intel website (https://ark.intel.com/content/www/us/en/ark/products/195436/intel-core-i510210u-processor-6m-cache-up-to-4-20-ghz.html)
Max Resolution (DP)‡
4096 x 2304@60Hz