Foundry is tremendously complicated and requires a huge time investment (in watching 30-minute youtube videos and getting real friendly with the techs on Foundry's Discord) to learn how to set up and run a game in it. But since the systems you've listed are specifically
not D&D
* and you also don't want Roll20, I would say try Foundry.
Haha. Yes. HarnMaster probably. Maybe Blood & Bone. Possibly Champions and/or Fantasy Hero. The only thing I really plan on playing in person in the foreseeable future is Star Frontiers, and that's because I invested in a Megamat and a bunch of starship minis for space combat (via Knight Hawks).
I will note that from this list, the only supported system I found was
HarnMaster 3 [Foundry v12].
You can see the supported systems
here.
Keep in mind that you need to have the correct version of Foundry for the system (i.e. HarnMaster is verified for V12, the latest version of Foundry is V13). You can download any version of Foundry with a Foundry license.
As mentioned already, until the point where you actually want players to join the game, it's a one-time fee. If you can't figure out the technical aspects of hosting, you may be paying a subscription fee to get hosted.
Depending on your fanciness and module use, you may also end up with module subscriptions on Patreon. However, the most notable paid module that I know of is tied to specific needs in D&D, so if you're not doing D&D this potential additional cost is pretty irrelevant.
That was what I meant by weighting Roll20's steep learning curve against utility. Roll20's isn't hard to learn, but it also isn't easy to learn and its suite of tools is kind of... meh (especially for what you pay and the amount of learning you have to put in). IME, anyway. Some of the other VTTs look like they require more learning up front but ultimately cost less money and provide more functionality.
From this comment I would say you are a future Foundry user.
*Foundry can be used to run D&D too. It just has a bunch of extra variables that will add to your learning time, add to the decisions you will have to make, and can potentially add to the cost. I'm not going over those here because OP doesn't sound like a D&D player.