Baseline (Widescreen) Solution & Issues
Use AlexBond's Worms Forts Launcherfiles available from the PC Gaming Wiki Community Files (search there).. Set Aspect: On to correct the aspect ratio. For the GOG.com version run WFLauncher.exe as an administrator (required due to the GOG.com version of the game being set to run as an administrator on launch).
Everything scales correctly. FMV cutscenes are stretched. Real-time cutscene letterboxing ends at the margins of the 4:3 area.
Part of the sliding inventory menu is always visible at wider aspect ratios (even during cutscenes). This does not affect gameplay (it still slides into position when triggered).
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
The HUD is centred for 4:3.
Eyefinity / Surround Specific Solution & Issues
Same as widescreen.
Some 3D elements may flicker during real-time cutscenes, especially in the area beyond the 4:3 limits. Some other strange cutscene behaviour will also be observed (such as off-screen worms mirroring the facial expressions of worms that are visible within the 4:3 area).
4k UHD Specific Solution & Issues