First language I came across that doesn't use a loanword for internet. How does it translate literally?
rhyng- (inter-) from rhwng (between) and -rwyd from rhwyd (a net).
In casual speech, people seem to use y we.
The word for the (World Wide) Web is 'Gwe' or 'Y We' (soft mutation after definite article') which just means 'the web'.
As a former IT teacher in a Welsh medium school I used be very pleased with the children talking about 'mynd ar y We' (going on the Web) rather than the incorrect 'go on the Internet'.
This usage is not correct. The World Wide Web is a subset of services using the Internet. Personally I was using the internet (e.g. email, telnet, ftp and even gopher - a precursor of http) since the mid eighties, several years before Berners-Lee invented the Web. There are a great many other services using the internet infrastructure that you would be wrong to describe as the Web (taking a few at random - ssh, ntp, wmts, and many many more). Use of The Web / Y We when the wider Internet / Rhyngrwyd is meant should be discouraged.
There is only 1 internet therefore shouldn't 'y ryngrwyd' be accepted? If not, then why isn't "an internet" accepted as the answer?
We can add 'an internet' as an alternative answer. There may be only one at the moment, but people may discuss others or a new one, perhaps.
('The internet' is y rhyngrwyd - ll- and rh- both resist mutation after y, un, yn and mor/cyn. This comes up in other sentences.)