There is another way, I thought. Seem to recall certbot offering it when failing here. If you want more details I can dig into it but it has you create a file in a .well-known and it’ll go check for it there.
Edit: as others mentioned the prerequisite here is that you’re also listening on port 80 somewhere.
Also, don’t forgot let’s encrypt will time you out if you ping too often.
Count me in! Switched to Linux Mint for my DD last month.
Only thing I’m missing is a very dead simple 3D modeling replacement for the Windows one (the others have a steep learning curve). I’ll have to find a browser based option…