Trying to apply D9 compatibility patch on Boostrap_mint theme

Problem/Motivation

Hello everyone,

I was trying to apply the updated_files-3146299-4.patch → from the previous issue 📌 Automated Drupal 9 compatibility fixes RTBC in order to fit with D9 compatibility. Unfortunately, I'm getting an error with my composer when I try to apply this patch:

Gathering patches for dependencies. This might take a minute.
  - Installing drupal/bootstrap_mint (5.0.0): Loading from cache
  - Applying patches for drupal/bootstrap_mint
    https://www.drupal.org/files/issues/2020-09-04/updated_files-3146299-4.patch (D9 compatibility)
   Could not apply patch! Skipping. The error was: Cannot apply patch https://www.drupal.org/files/issues/2020-09-04/updated_files-3146299-4.patch

I can see that in my bootstrap_mint.info.yml, the core: 8.x is commented. On the end of the file, these lines are set:

# Information added by Drupal.org packaging script on 2018-06-15
version: '8.x-5.0'
core: '8.x'
project: 'bootstrap_mint'
datestamp: 1529059435

So, I'm wondering if the previous patch can actually fix my compatibility problem with bootstrap_mint, which is:
"Add core_version_requirement: ^8 || ^9 to designate that the module is compatible with Drupal 9. See https://drupal.org/node/3070687."

Used versions:
Drupal 8.9.15
Boostrap Mint 5.0