Following Unity licencing changes a few people started naming engine alternatives and here follows a list of game engines and frameworks to use in Game Development, most are free and open-source but a few are commercial. These were taken from suggestions on this thread (https://mastodon.gamedev.place/@djlink/111052944661218945), so it was a community collaboration, I just gathered them all in one place, thanks to everyone who contributed.
Feel free to make PR with more things
Godot - https://godotengine.org
MonoGame - https://www.monogame.net/
FNA - https://fna-xna.github.io/
SDL - https://www.libsdl.org/
SFML - https://www.sfml-dev.org/
Adventure Studio - https://www.adventuregamestudio.co.uk/
bgfx - https://github.com/bkaradzic/bgfx
armory3d - https://armory3d.org/
ogre3d - https://www.ogre3d.org/
Ren'py - https://www.renpy.org/
TIC-80 - https://tic80.com/
Murder - https://github.com/isadorasophia/murder
Bevy Engine - https://bevyengine.org/
LÖVE2D - https://love2d.org/
libGFX - https://libgdx.com/
RayLib - https://www.raylib.com/
Defold - https://defold.com/
HaxeFlixel - https://haxeflixel.com/
Twine - https://twinery.org/
Enigma - https://enigma-dev.org/
Robust Toolbox - https://github.com/space-wizards/RobustToolbox
Solar2D - https://solar2d.com/
Phaser - https://phaser.io/
Tilengine - https://www.tilengine.org/
PlayCanvas - https://playcanvas.com/
Construct - https://www.construct.net/
RogueEngine - https://rogueengine.io/
GDevelop - https://gdevelop.io/
PyGame - https://www.pygame.org/
MelonJS - https://melonjs.org/
Allegro - https://liballeg.org/
Luxe - https://luxeengine.com/
Solarus - https://solarus-games.org/
nCine - https://ncine.github.io/
pyxel - https://github.com/kitao/pyxel
ursina engine - https://www.ursinaengine.org/
Arrow - The Game Narrative Design Tool - IF- https://mhgolkar.github.io/Arrow/
Inform 7 - IF - https://ganelson.github.io/inform-website/
Adventuron - IF - https://adventuron.io/
IfSpace - IF - https://www.ifspace.net/
OpenSludge - PnC - https://opensludge.github.io/
ngPAWS - IF - https://ngpaws.com/
FI-js - IF - http://baltasarq.github.io/fi-js/
TextEngine - IF - https://github.com/okaybenji/text-engine