If you want sound without spending jam hours on it, these two packs are free and drop straight into GDevelop (WAV and OGG both work):

• Essential UI SFX: 150 interface sounds, 30 events with 5 versions each, so clicks and confirms don't repeat.
  https://willosuna.itch.io/essential-ui-sfx
• Magic Spells SFX Lite: 30 spell sounds (fire, ice, lightning, shadow, holy, poison, shields, portals, summons).
  https://willosuna.itch.io/magic-spells-sfx-lite

Mono WAV, plus OGG versions for lighter web builds.

All of it is synthesized from code: no recordings, no third-party samples. Royalty free for commercial use, no credit required.

Credit is not required, but if you want to list it, "Willosuna" is fine. Good luck with the jam!

Update: there are now free pixel art UI kits too, if your game needs menus, bars or inventory slots:

• Pixel art UI kits (free Lite versions): Fantasy, Horror, Retro arcade, Cyberpunk neon and Cozy: panels, dialogue boxes, buttons, toggles, hearts, slots and bars, at native size and 4x.
• Pixel Cursors & Icons: 46 cursors and icons (hearts, coins, keys, weapons, UI symbols).
• Essential UI SFX: 150 menu and interface sounds, WAV + OGG.

Same deal: free for commercial use, no credit required.