Heck, I'd be happy to do this, but I'm swamped with business right now. I'm currently hosting a bunch of sites in the AWS/S3 realm. Easy to do and pretty darn inexpensive when no one likes you and no one visits your sites. However, at work, we leverage Databricks/Spark Apache in the AWS cloud and leverage many S3 buckets. My DevOps team ran up a bill for $12k last month and we're like in 10th place for team's DevOps bills in the company. What I'm saying is, costs can ramp up quickly depending on what features are leveraged.
AWS provides a TCO dashboard to show running costs. Maybe publish that and ask for donations to cover those costs?
Setting up a PHPbb forum is rather simple.
Anybody can do it.
However if you want to combine a forum with a photo hosting site and a wiki for trip report some development by a real programmer may be required.
Expect to pay at least $200-300/month for hosting (assuming programming and maintenance is done by volunteers).
Anyway, setting up such forum/site would require a lot of efforts.
I am not sure we have anybody willing to do this on Supertopo.