Hi michaelangelo_33,
Thanks for reaching out using Apple Support Communities. Here to help.
We understand you are not seeing the option to take a full-page screenshot in Safari.
This should still work as expected in iOS 14.5.1, as described in the user guide below in the section 'Take a full-page screenshot'
Take a screenshot or screen recording on iPhone
This feature also works with websites, documents, and emails. Can you see if this feature is working for you in other applications, such as Mail or Files?
The ability of this feature to work in Safari does depend on if Safari has loaded the full contents of the webpage. It may be helpful to clear browsing data and try again. This can be done in Settings > Safari > Clear History and Website Data.
Alternatively, you may be able to reach a similar result by saving the website as a PDF. This is done in the Share menu. Look for Options, choose 'Send As PDF', then share or save the file as desired.
If you continue to have issues, you may wish to send a bug report to Apple using the below link.
Apple Feedback
Hope this helps!