Domain registration already has a lot of rules around length, what characters can be where in the domain name (ex. no hyphens as the very first/last characters), ... I'm sure it'd be trivial to have a "no-repeating-spaces" rule or similar.

google.com [spaces] pwned.evilcorp.com it is

I just want a single contiguous space character so I don't have to suppress the space or substitute with an alternate character --also URL boxes can make it conspicuously obvious for better UI. And while they're at it, allow & (ampersand).

Maybe the location bar should accept the space but strip it? That would work for input if not reading the URL. Maybe only allowing single consecutive spaces to avoid the address spoofing example. I could go for that.

I would love & natively though. For my wedding (bride&groom.com for example) I looked into faking it with punycode but nothing was close enough, and anything other than an ampersand would have been too hard to input.

good think hyperlinks are typically underlined so there will be a large training line at the end

Unless someone turns off the underlining with a stylesheet.

Google search urls are typically long enough that they are shortened by ... At least on mobile