I haven't touched the html code on my website for 20 years.

Got an email today from google (googlebot is constantly crawling my site, for years). The email says:

Top Issues
Viewport not set
Text too small to read
Clickable elements too close together

I probably don't have a viewport command / statement anywhere in my pages. Is there a generic viewport statement that I can throw in that will work for anything hitting my site and maybe make google happy in this regard? My server doesn't pay any attention to what's hitting it, serves up the same html files to anything / everything.