You could also look into becoming an electrician. That touches on more high tech stuff than plumbing. And you get to flex your math skills as a master electrician. I think (hope) that there is a fairly rigorous certification for getting into electrical apprenticeship programs in every region. In the city where I grew up, they had to sit for exams in order to get to specific levels.

Edit to add: while both jobs have too much crawling through spiderwebs in crawlspaces for my tastes, electricians encounter orders of magnitude less poop than plumbers.

Every job gets a little more techie every year. I'm sure the master plumbers use some pretty sophisticated software to plan out the plumbing in a house.

Heck, just a simple job needs planning, billing, and more. All of which use computer systems.

Even just knowing logic and high end math is showing that you're not just a knucklehead looking to do the bare minimum.

Every bit of experience you had in a previous role can be used in the current one. Just spend a few minutes thinking of how it would work and use that in any interviews you get.

Just remember, even though most of these folks didn't go to university, doesn't mean they're any dumber than you are. If they're doing high quality work, they're probably just as smart, or smarter.