my users are HVAC dispatchers and they are not on any forum I can find

They are online, just not where you have been looking. For trades the actual gathering places tend to be Facebook groups with thousands of members, YouTube comment sections under specific repair videos, and manufacturer or distributor portals. None of those are indexed the way a forum is, so they feel invisible if you search from the outside.

The other channel that people ignore because it is unglamorous: the supply houses. The counter staff at a local distributor talk to every small firm in the area, every week. Two conversations there got me introduced to four owners, which is four more than six months of writing had produced.

Ring them. I know. But this is the sector where a phone call is normal and an email is suspicious, and dispatchers answer phones for a living.

I made forty calls over two weeks for a similar tool. Twenty-two never picked up, eleven were polite and short, six turned into a real conversation, and two of those became customers at the end. The script was: I built a thing for X, I am not selling today, can I ask you two questions about how you currently do Y. Nobody was rude. Several were pleased that anyone had asked.

The unexpected benefit was that after six of those calls I could describe the problem in their words instead of mine, and my landing page stopped sounding like software.

Trade associations, and specifically their local chapters rather than the national body. The national one wants sponsorship money you do not have. The local chapter has a meeting once a month with thirty owners in a room, a newsletter with no advertisers, and a programme secretary desperate for someone to speak for twenty minutes.

Speak about the problem, not the product. Bring the answer to a question they all have. You will get the room's attention and, more usefully, a list of names.

Worth considering that the reason there is no forum is that there is no community, and that changes your strategy rather than just your channel. Some markets are not communities, they are a list of businesses. In a list market you do not build an audience, you do outbound and you get referrals, and the winning asset is a customer who will take a phone call from a stranger and vouch for you.

Plan for that instead of waiting to find the room where they all hang out. That room may genuinely not exist.

One channel that works surprisingly well for trades and gets dismissed: search, but for the problem rather than the product. Nobody in that sector is searching for scheduling software. Plenty of them are searching for things like how to handle a no-show policy, or a template for a service agreement, or what to do when a technician's paperwork keeps arriving three days late.

Write four genuinely useful pages answering those, with a downloadable template on each. It is slow and it is not glamorous, but it accumulates and it does not require you to find the room.

Go to where the money is already moving. Whoever sells them their equipment, their insurance, their invoicing software, or their vans already has the list. A referral arrangement with one of those is worth more than any content you will write this year.