Install fails due to composer incompatibility

Trying to install VirtualBox, Vagrant and Homestead dev environment in Windows 10. Trying “vagrant up” results in:

    userfrosting:   Problem 1
    userfrosting:     - wikimedia/composer-merge-plugin dev-master requires composer-plugin-api ^1.1 -> found composer-plugin-api[2.0.0] but it does not match the constraint.
    userfrosting:     - wikimedia/composer-merge-plugin[v1.4.0, ..., v1.4.1] require composer-plugin-api ^1.0 -> found composer-plugin-api[2.0.0] but it does not match the constraint.
    userfrosting:     - wikimedia/composer-merge-plugin 1.5.x-dev is an alias of wikimedia/composer-merge-plugin dev-master and thus requires it to be installed too.
    userfrosting:     - Root composer.json requires wikimedia/composer-merge-plugin ^1.4.0 -> satisfiable by wikimedia/composer-merge-plugin[v1.4.0, v1.4.1, 1.5.x-dev (alias of dev-master)].
    userfrosting:
    userfrosting: You are using Composer 2, which some of your plugins seem to be incompatible with. Make sure you update your plugins or report a plugin-issue to ask them to support Composer 2.
    userfrosting: ERROR :: File `/home/vagrant/userfrosting/app/vendor/autoload.php` not found. This indicate that composer has not yet been run on this install. Install composer and run `composer install` from the project root directory. Check the documentation for more details.
    userfrosting: ERROR :: File `/home/vagrant/userfrosting/app/vendor/autoload.php` not found. This indicate that composer has not yet been run on this install. Install composer and run `composer install` from the project root directory. Check the documentation for more details.
    userfrosting: ERROR :: File `/home/vagrant/userfrosting/app/vendor/autoload.php` not found. This indicate that composer has not yet been run on this install. Install composer and run `composer install` from the project root directory. Check the documentation for more details.
    userfrosting: ERROR :: File `/home/vagrant/userfrosting/app/vendor/autoload.php` not found. This indicate that composer has not yet been run on this install. Install composer and run `composer install` from the project root directory. Check the documentation for more details.
    userfrosting:
    userfrosting:
    userfrosting: UserFrosting is ready at http://192.168.10.10/

Due to this error when I try to access UserFrosting at the above address I get “No input file specified.” which I am sure is because the “autoload.php” script mentioned above did not run.

Seems I need to install older versions of composer, but I have no clue where to start even after reading documentation. I have no Linux experience, never needed command-line functionality before, never used SSH before, never used composer before. I’ve developed PHP/MySQL systems before using XAMMP using Windows and this seemed very easy to do.

How do I fix this install issue? Where can I get up-to-speed on this environment? Or am I just better off going back to XAMMP which I am familiar with?

As described here, UF is currently not compatible with Composer 2. I opened an issue to fix it in Vagrant for next release : https://github.com/userfrosting/UserFrosting/issues/1134