vagrant up fails with cannot load winrm

Had the same issue: With Ubuntu Ubuntu 20.04.1 LTS running ruby 2.7.0p0 and Vagrant 2.2.6

The solution that worked for me -

$ vagrant plugin install winrm  
$ vagrant plugin install winrm-fs  
$ vagrant plugin install winrm-elevated (this additional error showed after the first two were installed)  

The winrm and winrm-fs gems are not packaged with Fedora or Debian. You can run:

$ vagrant plugin install winrm
$ vagrant plugin install winrm-fs

(i.e. vagrant plugin install, not gem install).

Note: Using Vagrant version 1.8.1, the winrm gem failed to install and this fixed it:

$ vagrant plugin install winrm --plugin-version 1.8.1
$ vagrant plugin install winrm-fs

Not sure what the problem was, but I fixed it by uninstalling vagrant with dnf, and installing the latest version from vagrantup.com. Seems winrm is included in the latest vagrant version.