Apache Rewrite to HTTPS only when supported by browser vhosts / htaccess

.htaccess

# I only have used it inside of my vhosts file, but I think it should also work in .htaccess

RewriteEngine on

# rewrite to https.
# -----------------
# %{HTTP:X-Forwarded-Proto} !https: This condition checks if the X-Forwarded-Proto header is not set to https. 
# The X-Forwarded-Proto #header is typically set by proxies or load balancers to indicate the original protocol 
# used for the request. By checking this header, # you can ensure that the redirect only occurs if the request 
# is not already using HTTPS.
RewriteCond %{HTTP:X-Forwarded-Proto} !https

# %{HTTP:Upgrade-Insecure-Requests} ^1$: This condition checks if the Upgrade-Insecure-Requests header is set to 1. 
# The Upgrade-Insecure-Requests header is sent by modern browsers that support HTTPS and can automatically upgrade 
# an insecure request to a secure one. By checking this header, you can verify if the browser supports HTTPS and 
# wants to upgrade the request to HTTPS.
RewriteCond %{HTTP:Upgrade-Insecure-Requests} ^1$

RewriteRule ^/?(.*) https://%{SERVER_NAME}/$1 [R=301,L]

This makes it possible to use your website with browsers which don't support https

Not sure if it also works for browsers which support an older version of https