What you are lacking is answered in your own post - experience of systems that are non-standard for regular home PCs.
From what I am reading most of your work is for personal clients or SMBs, most of which use very limited, software - as in, not many products. Larger companies and corporations use bespoke software or other Microsoft products that regular home users would never even hear of. The only way to know these is to use them in a lab or work for a company which does. Bear in mind that all the jobs you have seen are paid, if you are offering your skills for free, call the advertisers and ask if you can speak to the employer, advise while you don’t know product A, B or C, you are willing to give up your time, to be able to better yourself. If they have anything they can offer you, paid or unpaid. Just chat with them, let them know you are here and send over your resume for future, should they wish to revisit.
While you don’t have the experience of products outside of what you already know, you do have IT experience, that’s a start.
I would recommend you try to assist people with their queries on here, use the ‘answer questions’ at the top of this page and read through other peoples issues and offer your support and guidance. Whilst you wait for someone to reach out, you might as well show your skills off.
Use the platform like a visual resume, where people reading can see your skills.
Have you spoken to any local companies, schools or universities, either about direction or offering them your services, have you handed out any resumes or do you even have a current one?
Finally - my usual suggestion, if you do not currently have a lab, I’d get one, people here would be more than willing to set you homework tasks and there is even a category on here where people can discuss their labs and what they learn.
I’ve learned so much on here by participating in topics, maybe you will too.
Might also be worth going over some of the SW training https://community.spiceworks.com/learn/