I worked in engineering in the UK which due to the shortage of skilled workers allowed me to come and go as I pleased, either returning to a previous employer or finding a new one. I did an apprenticeship as a toolmaker and did a variety of jobs including many types of manual and CNC machining and as a machine and engine fitter.
This work is not union controlled as some trades seem to be in North America, although I was a member of a trades union in a couple of places and once you started an apprenticeship which was usually straight out of school at 16 you would be expected to finish it which would take 4-5 years.
In the UK at least any apprenticeship in a skilled manual job would lead to regular and possibly flexible employment, the building trades were particularly in demand but what the economy and jobs market will be like after covid has done its danmedest is anyones guess.

OP, what's conspicuously missing from your description is any indication what sort of work you really enjoy, thrive on, could commit to. That matters, particularly if you're hoping to work for a bit, then take off to travel, then return to the same job in a different setting. This would be much more difficult if you're working begrudgingly. I'd suggest finding work which suits you, then setting it up in a way which allows you to do whatever else you want with your life. Is should go without saying that this may change in time--both the work itself, and your other priorities.

You also seem to think that unions are the key, at least when it comes to skilled labor. I've done a lot of traveling over the years, from weekends thru multiple yearlong trips, and I've done most of it by virtue of self-employment. It's worth thinking about...but there again, it's a difficult prospect unless you're fairly passionate about what you're doing.

I've had several career phases, including a number of building trades and my current (self-employed) work in counseling. Each had its own barriers to entry, often involving massive outlays of money spent in education and training, but at other times requiring nothing more elaborate than willingness to abase myself doing unpleasant work for very little money. No unions were involved, although I did spend some time agitating for a union in a right-to-work state.

Hope that's helpful.

Brits have an advantage here I think.
All young travellers I know, weather they’re overlanders or backpackers, get a work visa for Australia, which is conveniently half way round the world. They leave the Uk and slowly head for Oz, either going east or west.

By the time they reach Oz their money is almost gone but they can work legally for a year and save up. Then they continue their slow journey home, continuing in the same direction - usually.
The Uk and Oz have reciprocal qualifications in place so that healthcare workers, teachers, trades and many other professions are free to work.
There are plenty of other jobs for non-skilled labour in Oz too, it’s the work visa that’s the important thing here.

I’ve always thought that there are 3 ways to do it.

1 - Digital nomad

2 - Have a profession that is well paid and has a strong agency supply history - in the UK that would be healthcare, teaching, lorry driving, IT, also trades such as bricklaying - many more I suspect. Work for a few years, save up , big trip then back home and repeat.

3 - Have a profession that is accepted in other countries, move to and work in different countries and use them as a springboard to travel in that part of the world. I suspect doctor or nurse is the best, perhaps IT but I know very little about that

My thoughts from the UK - not sure how helpful it is to an American though
Good Luck

Well speaking as an UK trained Electrician who moved down under, your UK qualifications DO NOT fully count, you need to have local licence (local regulations) which requires learning the local reg`s & sitting exams (its long & painful & costly) and until you have that local licence you cannot work as a 'qualified' Electrician.

In NZ you can apply for a temporary licence if you are a fully qualified electrician but you can only work under the supervision of a licensed electrician (bit like being a spotty apprentice all over again).

NZ & AUS qualifications are reciprocal in either country (ASNZ standards).

Mezo.

Yes, I guess I should have put “except electricians and possibly plumbers”.
I was thinking more of the wet trades - bricklaying, plastering and decorating.
Although I suspect things have changed even for those trades in Oz, as it has here in the UK.
Things were different in the mid 80s when I lived in Oz.

You laid it out nicely. I think I'm aiming for number 2. I do wonder about number 3, maybe trying to get engineering work abroad. Applying for work is a pain in the ass here let alone internationally. What route have you gone yourself?

I was self employed in the building trade - groundwork and brickwork - for 25 years. My wife was also self employed. We would have 4-7 weeks away every summer.
15 years ago we decided to retrain for jobs where we could live in other countries for a few years and use them as a springboard - for many reasons it didn’t pan out.
In hindsight we should have stuck to what we were doing and take longer off on occasions for bigger trips.
So there’s my answer to your original question.

There’s other advantages to having a ‘home base’ to return to:
A network of of friends and family for a myriad of things.
A network of work possibilities

The work your describing sounds pretty interesting. How long were you able to take off for? One option is to try to transition to a more hands on position with my mechanical eng. degree, although it might make more sense to to press the reset button completely.