To clarify the comments on the original question, there is a huge difference between attending a conference, speaking (uncompensated) at the conference, and being a headline item at the conference.
If you are simply attending a conference / meeting you can typically use a visitor visa. These are short-term, no-money-to-you events that happen daily, immigration has a standard process.
If you are doing something and getting paid by your home country / primary employer for it, most places will consider it to be the same. A company in their country hired a company in your country to do something, you are the something. Technicians, trainers etc. are similar.
If you are doing something and getting paid in the other country then you do not fall into the (slightly expanded) Tourist/Short term visitor category. A featured speaker would be considered "working" no matter how the money is handled. Another way to think about the distinction is "Can another person do the job just as well?" In the case of a technician, the answer is usually "yes".
Also note that immigration in many places (UK, AU, CA, US etc) interpret "compensation" rather broadly. If you received anything of value in exchange for your services, you are working. If the local contact is charging money for you specifically, you are working. Plenty of people have been bounced because their plans were building a deck in exchange for accommodation & entertainment (items that normally have value).
Notable examples you can find on YouTube:
A puppeteer was refused by the UK because he was intending to do a weekend seminar that charged participants. No work visa.
A chef was refused by AU because she had "tools of the trade" (kitchen knives) in her baggage. Knives are not a problem, but when you are a chef and also have 30 resumes in your bags......
A very large (all muscle), tattooed German man was going to AU to supervise work his company in Germany had been contracted to do. Immigration had no problem with the work - it fell under the technician principle. They refused him because of several criminal convictions and a decent amount of jail time, all of which he noted on his documents. And he probably scared them (although he was actually very pleasant and polite, that could probably change very quickly). They also said that if he applies for a formal visa through the embassy he will likely be accepted.