RPi's are still wildly overpriced & hard to find, and the Pi-alikes often (usually) have support issues (out of tree patches required, lots of opaque blobs, etc). I like my home-lab to be about learning new stuph, not being a beta site fighting underlying platform issues (aside: I confess that I do have one RPi-ish cluster (3 boards), but more and more it's being used for "I need some GPIO for this" and way less for 'compute'). As many folks have mentioned, pick up a couple of x86 mini PCs/SFF (new or refurbished depending on budget). FWIW...I've had luck with small, low power devices from Protectli, Seeed and Minis Forum. Problem solved; heartburn avoided.
Someone mentioned "r/homelab", which is pretty interesting/active if you can stomach Reddit.
VMware has a 'free' ESXi license for homelabs (no cost, many restrictions apply). It'll run on many/most of the small PCs out of the box; 7.0 ran perfectly on my Seeed Odessey. Yeah, I need to spend more time with the various newfangled OSS hypervisors, but I'm used to ESXi. Get off my lawn.
I personally think having a managed ethernet switch, particularly one you can do VLANs and netflow and/or port mirroring is helpful in a homelab. VLANs help you build more complex scenarios, and sometimes you really want more visibility about what's going on on the wire. Refurb Cisco or Dell switches work well (and tend to be very cheap), but also tend to be noisy and power inefficient. I don't have a ton of experience with the newer generation of probably more efficient 'desktop' smart switches like Zyxel, TP-Link and Ubiquity.