More assuming a bunch of stuff by me, but whatever. Besides his obvious employment history gap, judging by the comments he's made about his tech stack, he's stuck somewhere in mid-late 2000s. He was mentioning multi master mysql DBs, sshing to things by hand. Has he ever mentioned anything about cicd/devops? Terraform? Ansible? Chef?
There's still a huge market for the maintenance of legacy on-prem servers. Even big cloud-based saas companies are moving some things back on prem due to costs. However, those systems still want someone who can work in a team. How much project management is Null familiar will? Can he work in an agile environment? Can he create Arch specs, do documentation? Do requirements gathering?
There is a talent gap, but they are looking for people who can function in a team, even as a contractor you still need those soft skills. The "one man army" , method even if impressive, is not what tech is looking for now.
Has he ever mentioned anything about working with docker? k8s? Any devops at all? Any infrastructure as code? He uses telegram as his customer success portal, but does he have any SRE practices? Any monitoring or alerting? Does he have any SOC (security operations center), experience? Doesn't sound like he's pulling in logs into a central server? Does he have splunk or even an ELK stack is all open source? When he was hacked it looked like he was grepping server logs from an ssh terminal.
It seems like this was all built by him. How well would he do working on someone else's architecture and coming up to speed quickly to contribute? It's one things to manage and troubleshoot shit you built yourself, but doing that and then extending someone else's system is needed for most jobs.
Without work history or portfolios of enterprise systems, he will never get a senior (or above), position. In my completely uninformed opinion, he's set up an elaborate and highly functional proof of concept, but not an enterprise-level sustainable architecture.