Hi Luis,
I've just read your post. I see that Block Highlighter and Custom Crosshairs has been updated. I've just uploaded a mod that has the same functionality as Fulbright. It'll take up to 24 hours for it to be approved, but after that you can find it here: https://www.curseforge.com/minecraft/mc-mods/full-brightness-toggle
I hope it helps you play the game! Let me know if anything doesn't work as intended!
Kind regards,
Rick