I hate to say it, but the Pi is probably the only good option for a cheap (well, MSRP) ARM SBC with okayish software support. A lot of these no-name companies that produce ARM SBCs give them basically zero software support (save for maybe a buggy build of Debian or something) and expect the community do all the work. Have you checked out any x86 SBCs? The Rock Pi X is like $60 USD.

Looks like Rock Pi X has also been a victim of the chip/parts shortage: https://wiki.radxa.com/RockpiX

I've been thinking about wetting my feet with homelabbing a k8s cluster with used OptiPlex workstations. I wonder if Pi's will actually come back in stock or if some other SBC will eventually rise up and start eating away at the Pi's market share.

The question is "what functionality are you after?"

If you're after "I can run a small k8s cluster on it as part of a home lab", there are various x86 setups that you can build off of.

If you're after "I want a small device to tinker with" then things like https://onion.io ( https://community.onion.io ) may be a direction to look (and it isn't new - its been around for the better part of a decade https://news.ycombinator.com/item?id=12127161 )

tablets, mini pcs and stick pcs are findable in the $100 range, depending on your app this might be an option.

https://www.amazon.com/s?k=stick+pc&s=price-asc-rank

edit: tindie dot com and crowdsupply dot com are fun to browse around on