I had the forums hosted by others for a number of years.
We were shut down when Twi made complaints. This happened, I believe, twice.
So the solution was to have my own server.
And then we wouldn't be shut down.
I covered the costs out of my own pocket up until a few years back.
I moved from a physical server to a virtual server a number of years ago to reduce costs.
Donations are completely voluntary, you are under no obligation to donate.
I chose the most reliable companies, not the cheapest so there would be the least downtime.
Companies like SiteGround are great, but they can shut you down. I have to ensure that the site can't get shut down.
I've used PHPBB and I've found that Invision is more robust and have better support when you need it.