Gab’s founder, Andrew Torba, declined to comment on the site’s progress, telling me in a Gab message that “I don’t do interviews with fake news outlets.”

Instead, I spoke with Cody Wilson, a developer in Texas who is behind another alt-tech service. Mr. Wilson’s product, a crowdfunding site called Hatreon, was meant to give alt-right personalities and others a way to raise money for projects deemed too risqué for mainstream crowdfunding platforms such as Patreon and Kickstarter.

Hatreon got off to a fast start, with more than 400 creators raising about $25,000 per month on the platform. But lately, it has fallen into disrepair. According to Mr. Wilson, a major credit card company, which he declined to name, kicked Hatreon off its network last month, preventing many users from funding projects on the site and all but killing the company’s prospects for growth. Today, visitors to Hatreon are greeted by a message saying that “pledging is currently disabled while we upgrade our systems.”

Mr. Wilson, who does not describe himself as alt-right, said he has accepted that building a viable alt-tech business might be impossible, given the practical constraints.

“I don’t understand how any of them plan to be profitable,” he said.

Things aren’t going much better for WrongThink, which went online in late 2016 with aspirations of becoming a free-speech alternative to Facebook and Twitter. A year later, WrongThink has only about 7,000 registered members, according to the site’s founder, who goes by the username Bane Biddix.

Far-right activists have been trying to build alternative tech platforms for years, with little success. A decade ago, white nationalist websites with names like New Saxon and PodBlanc sprang up to compete with Myspace, Friendster, and the other social giants of the era. But most of those sites fizzled when their creators ran out of money or got into legal trouble. And none came close to reaching a large mainstream audience.

Granted, it is still the early days for this new wave of services, which are coming of age during the Trump years and could benefit from changing norms around P.C. culture and acceptable speech. Some alt-right leaders are hopeful that a coming “purge” on Twitter — their phrase for a change in the site’s hate speech policies, which Twitter plans to enforce beginning next week — will send scores of disgruntled users scurrying to alt-tech platforms.