Most modem-routers will allow you to re-assign the default webserver from port 80 to another port, so that you can use port 80 for port forwarding into your network.
Let’s Encrypt HTTP validation will only work with port 80. You cannot change that.
The timeout error generally refers to the condition where port 80 is blocked or not forwarded at all.
If you can’t get forwarding to work, then you have the option to use DNS validation. acme.sh supports DuckDNS to make that pretty easy.