VanishedOne: https://github.com/Kyuuhachi/Inevitable-Zero
'A mod for Trails from Zero that ports over the PS Vita-exclusive quests to the PC version. The translation is a work in progress.'

https://github.com/shinkiseki/MorePortraitsInZero
'Adds more portraits (Akatsuki, Azure, and completely new)'
The description only mentions the Steam version, but it doesn't seem to touch the .exe so hopefully it works with the GOG release.

https://www.reddit.com/r/Falcom/comments/y55sx6/trails_from_zero_difficulty_mod_official_rerelease/
'Trails From Zero difficulty mod'

VanishedOne: https://github.com/Kyuuhachi/Inevitable-Zero
'A mod for Trails from Zero that ports over the PS Vita-exclusive quests to the PC version. The translation is a work in progress.'

https://github.com/shinkiseki/MorePortraitsInZero
'Adds more portraits (Akatsuki, Azure, and completely new)'
The description only mentions the Steam version, but it doesn't seem to touch the .exe so hopefully it works with the GOG release.

https://www.reddit.com/r/Falcom/comments/y55sx6/trails_from_zero_difficulty_mod_official_rerelease/
'Trails From Zero difficulty mod'

EverNightX: Are the portraits from the vita version too?