When I Install and set as default. website encountered an unexpected error

I've successfully reproduced the issue on my machine, and created a patch to resolve it.
Please find the attached patch below, Thanks.

Hi i have apply patch for when install the theme website encountered an unexpected error because of the spaceless tag that is not to be supported after twig 2.7 now we can use {% apply spaceless %}{% endapply %} now the issue is fixed i have attached the applying patch screenshot below please review.

Patch #3 works well, But there are few more occurrences
Updated the patch and moving to RTBC.
Thank you.

I also faced the installation issue and was able to resolve it. This issue exists due to this line core: 8.x, it is valid for Drupal 8. We don't need this code simply remove this line and it solves the installation issue.
See this for info standard [ https://www.drupal.org/docs/develop/theming-drupal/defining-a-theme-with... →

I don't think the previous patch changes required in the theme. Please review anyone and suggest.

This is not related to the Spaceless tag, please create a separate issue for this.

This issue exists due to the drupal_get_path() function in the theme.theme file and it is deprecated. I have created a patch for this and attached the screenshot after fixing this issue.

Hello @bandanasharma I have tested this issue in Drupal 9.5.x.
I am also getting the error "The website encountered an unexpected error. Please try again later" when I install & set it as the default theme.
Then I apply patch #2 and again I check this issue.
Now the theme is installed successfully.

Also, I agree with @bandanasharma, there is no need for the previous patch, excluding patch #2.
I am sharing screenshots for reference.
Please review.
Thank you.

Patch @6 resolved the above issue.

Thanks to @bandanasharma.

This is issue if duplicate issue of https://www.drupal.org/project/status_zymphonies_theme/issues/3379038 🐛 drupal_get_path() function is not supported in drupal 10 RTBC .

So closing as duplicate.