Let me help to those who use the Rockstar launcher (Maybe it works also on other platforms, but I'm not sure)
Firstly, if your game is already updated and you have a backup in RPH you have to revert it to the supported version through RPH.
Then follow these steps:
1) Download this https://gta5mod.net/gta-5-mods/tools/no-gtavlauncher-2-0/
2) Extract No_GTAVLauncher.asi only into your GTA5 main directory (You need asi loader to work it properly)
3) Make shortuct to GTA5.exe (Anywhere, for instance on a desktop)
4) Add -scOfflineOnly to target in shortcut properties - like this "E:\GTA\Grand Theft Auto V\GTA5.exe" -scOfflineOnly
5) You are done with files
6) Start RPH and immediately after start GTA through that created shortcut and it should work!