Working only in bash shell only

[YouROK]

Describe the bug
If a default shell other than bash is installed on the server, the installation fails.

To Reproduce
Steps to reproduce the behavior:
On vps server:

apt install fish
chsh
# enter "/usr/bin/fish"

On host in AmneziaVPN select Self-hosted VPN and all next. VPN protocol I select awg.
And click Install button

Expected behavior
Execute scripts in the bash, not in the default shell.

Screenshots

Desktop (please complete the following information):

• OS: MacOS 15.0.1
• Version 4.8.1.9

Server (please complete the following information):

• OS: Debian 12

[vanyasem]

The scripts should specify a shebang #!/usr/bin/env bash instead of relying on the default shell

check_user_in_sudo.sh fails to get executed on fish shell, resulting in an Error 205: ServerUserNotInSudo:

$ CUR_USER=$(whoami);\
  groups $CUR_USER
fish: Unsupported use of '='. In fish, please use 'set CUR_USER $(whoami)'.