If the fab isn't that expensive, all the more reason to learn how to do it proficiently for free, no? Even if it doesn't get produced it seems like a good learning project.
absolutely! but that already existed. (free tools that don't result in something that can be fabbed)
what you would get out of this is access to a google-promoted open source PDK. It's specific to SkyWater so "open source" don't mean a whole lot, not today anyway. The available libraries are very immature. It's clearly a nice promotion for SkyWater, one I am enthusiastic about, but nonetheless not the shimmering beacon you're looking for.
You already know this: time is your most precious commodity. Don't bumble your way through a thinly disguised and immature FOSS offering. Cadence Virtuoso online training is just $3k per seat per year[1]. That said, I'm completely talking out of my rear. I've no idea if the training is actually useful without having a license for Virtuoso, where the webs say license costs are 6 figures per seat. I'd enroll in a university program to get access ... [2]
I just suggest this based on your stated goals, to be able to have enough proficiency to use professionally. Certainly you don't need 10,000 hours, and some of that is amortized by related experience, but time is your #1 enemy here, not money. Any money you can spend to jumpstart things is money well spent. OTOH if you just want to enjoy exploring IC design in a noncommittal hobbyist way, as a learning "experience" ala MasterClass, then this project does seem an excellent starting point.
SkyWater is a "trusted foundry", whatever that means, apparently completely US-based. Therefore, I think the most valuable thing that could ultimately (say 5 years hence) come out of this would be for OpenTitan to be "ported" to ASIC and to the SkyWater process. 130nm is large but for this application, for IoT in general, for anything not a mobile handset, it would be powerful. Imagine a Raptor TALOS workstation with an OpenTitan RoT! Or, your own design PCIe card with your own fabbed and X-Ray verifiable RoT. Powerful.
hate to tell you this, but probably not. there are only 40 slots. those are going to quickly be eaten by people that already know how to do this.
the fab isn't the expensive part anyway. you can get a small run of ASICs done for a few single digit $thousand