Are there any providers of 1U personal colos these days?

Not just personal but full-fledged business colo: https://www.m5hosting.com/, with data centers in San Diego, Austin, and Munich.

I've been using M5 Hosting for almost 20 years and find them to be outstanding. I highly recommend M5 Hosting.

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Chris Paul | Rex Consulting | https://www.rexconsulting.net